Recording power determination method and device

ABSTRACT

A recording power determination method for determining a recording power of an optical beam for recording data on an information storage medium includes the steps of recording test data on the information storage medium at a plurality of test recording powers; reading the test data recorded at each test recording power, generating a signal, and measuring a modulation factor of the signal corresponding to each test recording power; calculating a product of an n&#39;th power of each test recording power and the corresponding modulation factor, thereby obtaining a plurality of products corresponding to the plurality of test recording powers, where n is a value of exponent and is a real number other than 1; calculating a first recording power based on the correlation between the plurality of test recording powers and the plurality of products; and calculating the recording power based on the first recording power.

This is a continuation of International Application PCT/JP2005/001140,with an international filing date of Jan. 27, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording power determination methodand a recording power determination device for determining a recordingpower for recording data on an information storage medium.

2. Description of the Related Art

Optical discs are known as information storage mediums for datarecording. An optical disc apparatus irradiates an optical disc with anoptical beam to record data or to reproduce data recorded on the opticaldisc. Even if optical discs and optical disc apparatuses are produced inthe same manner, there are individual differences among the opticaldiscs and the optical disc apparatuses. Due to the individualdifferences, there may occur a problem that data cannot be properlyrecorded on an optical disc or data recorded on an optical disc cannotbe properly reproduced.

As one method for preventing such a problem, it is known to determine arecording power which is appropriate for an individual optical disc andan individual optical disc apparatus when, for example, mounting anoptical disc.

FIG. 16 is a schematic view showing a general optical disc 601. As shownin FIG. 16, the optical disc 601 has a track 602 formed thereinspirally. By irradiating the track 602 with an optical beam having amodified recording power, a plurality of marks and a plurality of spacesare formed on the track 602. Thus, data is recorded. The optical disc601 includes a user data area used for data recording by the user and arecording power determination area used for determining a recordingpower of the optical beam. The recording power determination area isprovided in an area other than the user data area (specifically, aninnermost area or an outermost area of the optical disc 601).

FIG. 17 is a schematic view showing a conventional optical discapparatus 700. The optical disc apparatus 700 includes an optical head702, a reproduction section 704, a demodulation/ECC (Error CorrectingCode) circuit 706, a recording power determination section 708, arecording power setting section 710, a laser driving circuit 712, and arecording data generation section 714.

When the optical disc 601 is mounted on the optical disc apparatus 700,the type of the optical disc 601 is identified, and the optical disc 601is rotated. The optical head 702 has a semiconductor laser (not shown).While being rotated, the optical disc 601 is irradiated with an opticalbeam emitted from the semiconductor laser of the optical head 702.

For recording data on the optical disc 601, the optical head 702irradiates the optical disc 601 with an optical beam having apredetermined recording power to form marks on the optical disc 601. Inthis example, data of the Run Length Limited (1,7) modulation system isrecorded by a mark edge recording method. In this case, seven types ofmarks and spaces are formed on the optical disc 601 on the basis ofreference cycle T, which is 2T at the shortest and 8T at the longest.

For reading data from the optical disc 601, the optical head 702irradiates the optical disc 601 with an optical beam having areproduction power which is smaller than the recording power andreceives light reflected by the optical disc 601. The optical head 702performs optical/electric conversion on the received light to generate asignal indicating the data recorded on the optical disc 601. Thereproduction section 704 measures a modulation factor of the signalgenerated by the optical head 702, and digitizes the signal generated bythe optical head 702. The modulation factor will be described later withreference to FIG. 19.

The demodulation/ECC circuit 706 demodulates the signal digitized by thereproduction section 704 and corrects errors. The recording powerdetermination section 708 determines the recording power for recordingthe data based on the modulation factor measured by the reproductionsection 704. The recording power setting section 710 sets the recordingpower determined by the recording power determination section 708 in thelaser driving circuit 712. The recording data generation section 714generates data to be recorded on the optical disc 601. The laser drivingcircuit 712 drives the optical head 702 to record the data generated bythe recording data generation section 714 on the optical disc 601 at therecording power set by the recording power setting section 710.

FIG. 18 is a schematic view showing the reproduction section 704 in theconventional optical disc apparatus 700. As shown in FIG. 18, thereproduction section 704 includes a preamplifier 801, a sampling andholding circuit 802, an A/D converter 803, an arithmetic operator 804,and a binary data generation section 805.

The binary data generation section 805 digitizes the signal generated bythe optical disc 702 to generate digitized data (binary data), andoutputs a signal 705 indicating the binary data to the demodulation/ECCcircuit 706 and the recording power determination section 708.

The preamplifier 801 amplifiers the signal generated by the optical head702. The sampling and holding circuit 802 samples the signal amplifiedby the preamplifier 801 and holds the peak value and the bottom value ofthe signal. The A/D converter 803 digitizes the peak value and thebottom value held by the sampling and holding circuit 802. Thearithmetic operator 804 performs an arithmetic operation on thedigitized peak value and bottom value to obtain a modulation factor.

FIG. 19 is a schematic view showing a waveform of the signal which isoutput from the preamplifier 801. As shown in FIG. 19, the modulationfactor is represented by (A−B)/A, where amplitude A is the amplitudefrom the signal level when no optical beam is emitted by thesemiconductor laser of the optical head 702, or the signal level when noinfluence is exerted by the light reflected by the optical disc 601 eventhough the optical disc 601 is irradiated with an optical beam having areproduction power emitted by the semiconductor laser of the opticalhead 702, to the signal level corresponding to the mark; and amplitude Bis the amplitude from the signal level when no optical beam is emittedby the semiconductor laser of the optical head 702 to the signal levelcorresponding to the space.

Returning to FIG. 17, a conventional recording power determinationmethod will be described.

On the optical disc 601, a constant parameter is recorded to be used fordetermination of the recording power. The optical head 702 generates asignal 703 indicating the constant parameter (hereinafter, referred toas a “predetermined value”) read from the optical disc 601, and outputsthe signal 703 to the reproduction section 704. The binary datageneration section 805 of the reproduction section 704 generates thebinary signal 705 obtained by binarizing the signal 703 indicating thepredetermined value, and outputs the signal 705 to the recording powerdetermination section 708.

The recording power setting section 710 sets a test recording power ofthe optical beam in the laser driving circuit 712. The recording powersetting section 710 sets eight different test recording powers A throughH. In this example, the test recording power A is the largest power, andthe test recording powers become smaller from the test recording power Btoward the test recording power H.

The recording data generation section 714 generates test data, andoutputs a signal 715 indicating the generated test data to the laserdriving circuit 712. The laser driving circuit 712 drives the opticalhead 702 to record the test data over substantially one circle of thetrack continuously from a predetermined position in the recording powerdetermination area of the optical disc 601. The recording datageneration section 714 generates the test data such that the opticalhead 702 continuously forms 8T marks and 8T spaces on the optical disc601. The test data is repeatedly recorded over substantially one circleof the optical disc 601 at the test recording powers A through H. FIG.20 shows areas of the optical disc 601 corresponding to the testrecording powers A through H with letters “A” through “H”.

When the recording of the test data is finished, the optical head 702irradiates the optical disc 601 with an optical beam having areproduction power. By this, the test data recorded on the track isread, and a signal indicating the test data is generated. The amplitudeof the signal generated by the optical head 702 changes in accordancewith whether or not the marks are formed on the optical disc 601. Thesignal 703 generated by the optical head 702 is input to thereproduction section 704.

Returning to FIG. 18, the preamplifier 801 of the reproduction section704 amplifies the signal 703. The sampling and holding circuit 802 holdsthe peak value and the bottom value of the signal amplified by thepreamplifier 801. The A/D converter 803 digitizes the peak value and thebottom value of the signal held by the sampling and holding circuit 802.The arithmetic operator 804 performs an arithmetic operation on thedigitized peak value and bottom value to obtain the modulation factor ofthe signal. Since the amplitude of the signal 703 is different inaccordance with the test recording powers A through H, the modulationfactor is also different in accordance with the test recording powers Athrough H. The arithmetic operator 804 generates a signal 707 indicatingthe modulation factors of the signal, and outputs the signal 707 to therecording power determination section 708.

The recording power determination section 708 determines the recordingpower based on the modulator factors corresponding to the test recordingpowers A through H by one of two conventional recording powerdetermination methods described below.

FIG. 21 shows a view for describing a first conventional recording powerdetermination method, and is a graph illustrating the relationshipbetween the test recording power and the modulation factor. According tothe first conventional recording power determination method, therecording power determination section 708 selects a recording power P0corresponding to a modulation factor M0 based on the correlation betweenthe plurality of test recording powers and a plurality of modulationfactors corresponding to the plurality of test recording powers. Therecording power determination section 708 calculates a product of therecording power P0 and a predetermined value read from the optical disc601 and thus determines the recording power used for recording data. Therecording power determination section 708 outputs a signal 709indicating the calculated recording power to the recording power settingsection 710.

FIG. 22 shows a view for describing a second conventional recordingpower determination method, and is a graph illustrating the relationshipbetween (i) the test recording power and (ii) the product of themodulation factor and the recording power. According to the secondconventional recording power determination method, the recording powerdetermination section 708 calculates a product of each of the pluralityof test recording powers and a modulation factor corresponding thereto,and thus creates an approximate line indicating the correlation between(i) the test recording power and (ii) the product of the modulationfactor and the test recording power. Then, the recording powerdetermination section 708 obtains a recording power Pthr at which theproduct is 0 on the approximate line. Next, the recording powerdetermination section 708 calculates a product of the recording powerPthr and a predetermined value read from the optical disc 601, anddetermines the recording power used for recording data. The recordingpower determination section 708 outputs a signal 709 indicating thecalculated value to the recording power setting section 710.

However, an appropriate recording power cannot be determined either bythe first conventional recording power determination method or thesecond conventional recording power determination method.

In the case that the recording power determination section 708determines the recording power according to the first conventionalrecording power determination method, the recording power determinationsection 708 cannot determine an appropriate recording power when, forexample, there is a relative tilt between the optical disc 601 and theoptical head 702. Hereinafter, with reference to FIG. 23, the recordingpower when there is such a tilt will be described.

FIG. 23 is a graph illustrating the relationship between the recordingpower and the modulation factor. In the graph of FIG. 23, a solid line1101 represents the result obtained when there is no tilt at the time ofdata recording or at the time of reading of the recorded data. A solidline 1102 represents the result obtained when there is a tilt at thetime of data recording, but there is no tilt at the time of datareading. A solid line 1103 represents the result obtained when there isa tilt both at the time of data recording and at the time of datareading. The modulation factor is smaller when there is a tilt than whenthere is no tilt. In the case where there is no tilt at the time of datareading but there is a tilt at the time of data recording, themodulation factor corresponding to the recording power H, which issmallest among the eight recording powers, cannot be measured.Similarly, in the case where there is a tilt both at the time of datarecording and at the time of data reading, the modulation factorcorresponding to the recording power H cannot be measured.

Test data is recorded and read before user data is recorded. The testdata is read immediately after being recorded. Accordingly, when thetest data is recorded and read while there is a relative tilt, theresult represented by the solid line 1103 in FIG. 23 is obtained. Whendetermining the recording power by the first conventional recordingpower determination method, the recording power determination section708 selects a recording power P1103 corresponding to the modulationfactor M0. This result is influenced by the tilt at the time of testdata recording and also by the tilt when the test data is read(hereinafter, referred to as “at the time of test data reading”).

In the case where there is a tilt at the time of test data recording, itis considered that there is a tilt also at the time of user datarecording. However, there is not necessarily a tilt at the time of userdata reading. It is very rare that the user data is read immediatelyafter being recorded. In many cases, the user data is read by anotheroptical disc apparatus or after the optical disc is re-mounted on theoptical disc apparatus. Therefore, there is no tilt at the time of userdata reading. Accordingly, for determining the recording power, only theinfluence of the tilt at the time of test data recording needs to beconsidered. It is not necessary to consider the influence of the tilt atthe time of test data reading. Therefore, the recording power whichshould be selected when there is a relative tilt is not the recordingpower P1103 but is a recording power P1102 in FIG. 23. When determiningthe recording power by the first conventional recording powerdetermination method, the recording power determination section 708selects the recording power P1103, which is larger than the recordingpower P1102. Therefore, the optical head 702 records data with anunnecessarily large power. As a result, by the first conventionalrecording power determination method, the optical disc 601 isdeteriorated unnecessarily quickly by repeated recording.

When using the second conventional recording power determination methodfor determining the recording power, the following occurs as shown inFIG. 24. When the recording power determination section 708 selects fourlarger test recording powers among the eight test recording powers andcreates an approximate line indicating the correlation between (i) eachof these four test recording powers and (ii) the product of themodulation factor and each of these four recording powers, the recordingpower at which the product is 0 on the approximate line is the recordingpower Pthr1. By contrast, when the recording power determination section708 selects four smaller test recording powers among the eight testrecording powers and creates an approximate line indicating thecorrelation between (i) each of these four test recording powers and(ii) the product of the modulation factor and each of these fourrecording powers, the recording power at which the product is 0 on theapproximate line is a recording power Pthr2.

As is clear from FIG. 24, the recording power at which the product is 0on the approximate line is significantly different in accordance withthe test recording power. Namely, when determining the recording powerby the second conventional recording power determination method, therecording power to be determined is significantly different depending onthe test recording power which is used for recording the test data anddepending on the test recording power, the result of which is used fordetermining the recording power. Accordingly, when using the secondconventional recording power recording method, the recording powerdetermination section 708 cannot uniquely determine an appropriaterecording power. In addition, when the recording power determinationsection 708 determines a recording power larger than an appropriaterecording power, the optical disc is deteriorated unnecessarily quickly.By contrast, when the recording power determination section 708determines a recording power smaller than an appropriate recordingpower, the data cannot be recorded properly on the optical disc.

The present invention, made in light of the above-described problems,has an object of providing a recording power determination method and arecording power determination device for determining an appropriaterecording power.

SUMMARY OF THE INVENTION

A recording power determination method according to the presentinvention, for determining a recording power of an optical beam forrecording data on an information storage medium, comprises a test datarecording step of recording test data on the information storage mediumat a plurality of test recording powers; a modulation factor measuringstep of reading the test data recorded at each of the plurality of testrecording powers, generating a signal, and measuring a modulation factorof the signal corresponding to each of the plurality of test recordingpowers; a product obtaining step of calculating a product of an n'thpower of each of the plurality of test recording powers and themodulation factor corresponding thereto, thereby obtaining a pluralityof products corresponding to the plurality of test recording powers,where n is a value of exponent and is a real number other than 1; afirst recording power calculating step of calculating a first recordingpower based on the correlation between the plurality of test recordingpowers and the plurality of products; and a recording power calculatingstep of calculating the recording power based on the first recordingpower.

In one embodiment, the first recording power calculating step includesthe step of creating an approximate line indicating the correlationbetween the plurality of test recording powers and the plurality ofproducts, and calculates the first recording power at which the productis 0 on the approximate line.

In one embodiment, in the product obtaining step, the value of exponentn is 2.

In one embodiment, the recording power determination method furthercomprises a value reading step of reading a value recorded on theinformation storage medium. The information storage medium has a valueof Pind, a value of ρ and a value of κ recorded thereon; the valuereading step includes the step of reading the value of Pind, the valueof ρ and the value of κ; the test data recording step includes the stepof setting a range of the plurality of test recording powers to be arange of 0.9 times to 1.1 times the value of Pind; the first recordingpower calculating step includes the step of creating an approximate lineindicating the correlation between the plurality of test recordingpowers and the plurality of products, and calculating the firstrecording power at which the product is 0 on the approximate line; andthe recording power calculating step includes the step of calculating aproduct of the first recording power, (−1/(the value of κ)+2) and thevalue of ρ.

In one embodiment, the recording power determination method furthercomprises a value reading step of reading a value recorded on theinformation storage medium. The information storage medium has the valueof exponent n recorded thereon; the value reading step includes the stepof reading the value of exponent n; and the product obtaining stepincludes the step of using the read value of exponent n.

In one embodiment, the test data recording step includes the step ofrecording the test data such that the signal generated in the modulationfactor measuring step includes a plurality of single cycle signals.

In one embodiment, the information storage medium has a plurality ofmarks and a plurality of spaces formed thereon by the optical beam whichhas been modulated; and the test data recording step includes the stepof forming the plurality of marks such that an amplitude of the signalgenerated in the modulation factor measuring step is substantially thesame as the amplitude of the longest mark among the plurality of marksformed on the information storage medium.

In one embodiment, the information storage medium has a plurality oftracks concentrically or spirally formed therein.

In one embodiment, the product obtaining step includes the step ofobtaining a plurality of products corresponding to the plurality of testrecording powers regarding each of a plurality of values provided as thevalue of exponent n; the recording power determination method furthercomprises a value determining step of calculating a linearity of thecorrelation between the plurality of test recording powers and theplurality of products regarding each of the plurality of values, therebycalculating a plurality of linearities corresponding to the plurality ofvalues, and determining one of the plurality of values which correspondsto the highest linearity; and the first recording power calculating stepincludes the step of calculating the first recording power using theplurality of products corresponding to the plurality of test recordingpowers regarding the one of the plurality of values which corresponds tothe highest linearity.

In one embodiment, the plurality of values include a first value and asecond value; and the first value is 2, and the second value is 3.

In one embodiment, the recording power determination method furthercomprises a value reading step of reading a value recorded on theinformation storage medium. The information storage medium has a valueof Pind, a value of ρ and a value of κ recorded thereon; the valuereading step includes the step of reading the value of Pind, the valueof ρ and the value of κ; the test data recording step includes the stepof setting a range of the plurality of test recording powers to be arange of 0.9 times to 1.1 times the value of Pind; and the firstrecording power calculating step includes the step of creating anapproximate line indicating the correlation between the plurality oftest recording powers and the plurality of products, and calculating thefirst recording power at which the product is 0 on the approximate line.

In one embodiment, the recording power calculating step includes thesteps of, in the case where the linearity when the value of exponent nis 2 is higher than the linearity when the value of exponent n is 3,calculating a product of the first recording power, (−1/(the value ofκ)+2) and the value of ρ; and in the case where the linearity when thevalue of exponent n is 3 is higher than the linearity when the value ofexponent n is 2, calculating a product of the first recording power,(3×(the value of κ)−2)/(2×(the value of κ)−1) and the value of ρ.

In one embodiment, the plurality of values include a first value and asecond value; and the value determining step includes a first testrecording power group setting step of, regarding the first value,selecting at least two test recording powers from the plurality of testrecording powers, and setting a first test recording power groupincluding the selected at least two test recording powers; a firstgradient calculating step of creating a first straight line based on allthe test recording powers included in the first test recording powergroup and the products corresponding to all the test recording powersincluded in the first test recording power group, and calculating afirst gradient of the first straight line; a second test recording powersetting step of, regarding the first value, selecting at least two testrecording powers which are not completely the same as the at least twotest recording powers included in the first test recording power group,from the plurality of test recording powers, and setting a second testrecording power group including the selected at least two test recordingpowers; a second gradient calculating step of creating a second straightline based on all the test recording powers included in the second testrecording power group and the products corresponding to all the testrecording powers included in the second test recording power group, andcalculating a second gradient of the second straight line; a first ratioobtaining step of obtaining a first ratio corresponding to the firstvalue based on the first gradient and the second gradient; a third testrecording power group setting step of, regarding the second value,selecting at least two test recording powers from the plurality of testrecording powers, and setting a third test recording power groupincluding the selected at least two test recording powers; a thirdgradient calculating step of creating a third straight line based on allthe test recording powers included in the third test recording powergroup and the products corresponding to all the test recording powersincluded in the third test recording power group, and calculating athird gradient of the third straight line; a fourth test recording powergroup setting step of, regarding the second value, selecting at leasttwo test recording powers which are not completely the same as the atleast two test recording powers included in the third test recordingpower group, from the plurality of test recording powers, and setting afourth test recording power group including the selected at least twotest recording powers; a fourth gradient calculating step of creating afourth straight line based on all the test recording powers included inthe fourth test recording power group and the products corresponding toall the test recording powers included in the fourth test recordingpower group, and calculating a fourth gradient of the fourth straightline; a second ratio obtaining step of obtaining a second ratiocorresponding to the second value based on the third gradient and thefourth gradient; and a comparing step of comparing the first ratio andthe second ratio.

In one embodiment, the first test recording power group setting stepincludes the step of selecting two largest test recording powers amongthe plurality of test recording powers; the second test recording powergroup setting step includes the step of selecting two smallest testrecording powers among the plurality of test recording powers; the thirdtest recording power group setting step includes the step of selectingtwo largest test recording powers among the plurality of test recordingpowers; and the fourth test recording power group setting step includesthe step of selecting two smallest test recording powers among theplurality of test recording powers.

In one embodiment, the recording power determination method furthercomprises the steps of calculating a first average power indicating anaverage of all the plurality of test recording powers regarding thefirst value; and calculating a second average power indicating anaverage of all the plurality of test recording powers regarding thesecond value. The first test recording power group setting step includesthe step of selecting the test recording powers to be included in thefirst test recording power group from the plurality of test recordingpowers, such that an average of the test recording powers included inthe first test recording power group is larger than the first averagepower; the second test recording power group setting step includes thestep of selecting the test recording powers to be included in the secondtest recording power group from the plurality of test recording powers,such that an average of the test recording powers included in the secondtest recording power group is smaller than the first average power; thethird test recording power group setting step includes the step ofselecting the test recording powers to be included in the third testrecording power group from the plurality of test recording powers, suchthat an average of the test recording powers included in the third testrecording power group is larger than the second average power; and thefourth test recording power group setting step includes the step ofselecting the test recording powers to be included in the fourth testrecording power group from the plurality of test recording powers, suchthat an average of the test recording powers included in the fourth testrecording power group is smaller than the second average power.

In one embodiment, the recording power determination method furthercomprises the step of recording the one of the plurality of values whichcorresponds to the highest linearity on the information storage medium.

In one embodiment, the information storage medium has identificationinformation recorded thereon for identifying the information storagemedium; and the recording power determination method further comprisesthe step of storing the identification information, and the one of theplurality of values which corresponds to the highest linearity andcorresponds to the identification information, in an identificationinformation storage section.

In one embodiment, the recording power determination method furthercomprises the step of reading the identification information recorded onthe information storage medium. The product obtaining step includes thestep of determining whether or not the read identification informationis the same as the identification information stored in theidentification information storage section, and when the readidentification information is determined to be the same as theidentification information stored in the identification informationstorage section, using the value corresponding to the identificationinformation stored in the identification information storage section.

In one embodiment, the identification information includes dataindicating a manufacturer or a lot of the information storage medium.

A program according to the present invention causes an informationrecording apparatus to perform the steps of the above-describedrecording power determination method.

A recording power determination device according to the presentinvention, for determining a recording power of an optical beam usedwhen a recording section records data on an information storage medium,the device, comprises an input section for receiving a signal indicatinga plurality of modulation factors corresponding to a plurality of testrecording powers; a calculation section for calculating a product of ann'th power of each of the plurality of test recording powers and themodulation factor corresponding thereto, so as to obtain a plurality ofproducts corresponding to the plurality of test recording powers,calculating a first recording power based on the correlation between theplurality of test recording powers and the plurality of products, andcalculating the recording power based on the first recording power,where n is a value of exponent and is a real number other than 1; and anoutput section for outputting a signal indicating the recording powercalculated by the calculation section to the recording section.

In one embodiment, the calculation section creates an approximate lineindicating the correlation between the plurality of test recordingpowers and the plurality of products, and calculates the first recordingpower at which the product is 0 on the approximate line.

In one embodiment, the value of exponent n is 2.

In one embodiment, the input section receives a signal indicating avalue of Pind, a value of ρ, and a value of κ; the output sectionoutputs a signal indicating the test recording powers in a range of 0.9times to 1.1 times the value of Pind to the recording section; and thecalculation section creates an approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products, calculates the first recording power at which theproduct is 0 on the approximate line, and calculates a product of thefirst recording power, (−1/(the value of κ)+2) and the value of ρ, so asto calculate the recording power.

In one embodiment, the input section receives a signal indicating thevalue of exponent n; and the calculation section uses a value ofexponent n.

In one embodiment, the calculation section obtains a plurality ofproducts corresponding to the plurality of test recording powersregarding each of a plurality of values provided as the value ofexponent n, calculates a linearity of the correlation between theplurality of test recording powers and the plurality of productsregarding each of the plurality of values, so as to calculate aplurality of linearities corresponding to the plurality of values,determines one of the plurality of values which corresponds to thehighest linearity, and calculates the first recording power using theplurality of products corresponding to the plurality of test recordingpowers regarding the one of the plurality of values which corresponds tothe highest linearity.

In one embodiment, the plurality of values include a first value and asecond value; and the first value is 2, and the second value is 3.

In one embodiment, the input section receives a signal indicating avalue of Pind, a value of ρ, and a value of κ; the output sectionoutputs a signal indicating the test recording powers in a range of 0.9times to 1.1 times the value of Pind to the recording section; and thecalculation section creates an approximate line based on the correlationbetween the plurality of test recording powers and the plurality ofproducts, and calculates the first recording power at which the productis 0 on the approximate line.

In one embodiment, in the case where the linearity when the value ofexponent n is 2 is higher than the linearity when the value of exponentn is 3, the calculation section calculates a product of the firstrecording power, (−1/(the value of κ)+2) and the value of ρ; and in thecase where the linearity when the value of exponent n is 3 is higherthan the linearity when the value of exponent n is 2, the calculationsection calculates a product of the first recording power, (3×(the valueof κ)−2)/(2×(the value of κ)−1) and the value of ρ.

In one embodiment, the plurality of values include a first value and asecond value; and the calculation section, regarding the first value,selects at least two test recording powers from the plurality of testrecording powers, and sets a first test recording power group includingthe selected at least two test recording powers; creates a firststraight line based on all the test recording powers included in thefirst test recording power group and the products corresponding to allthe test recording powers included in the first test recording powergroup, and calculates a first gradient of the first straight line;regarding the first value, selects at least two test recording powerswhich are not completely the same as the at least two test recordingpowers included in the first test recording power group, from theplurality of test recording powers, and sets a second test recordingpower group including the selected at least two test recording powers;creates a second straight line based on all the test recording powersincluded in the second test recording power group and the productscorresponding to all the test recording powers included in the secondtest recording power group, and calculates a second gradient of thesecond straight line; obtains a first ratio corresponding to the firstvalue based on the first gradient and the second gradient; regarding thesecond value, selects at least two test recording powers from theplurality of test recording powers, and sets a third test recordingpower group including the selected at least two test recording powers;creates a third straight line based on all the test recording powersincluded in the third test recording power group and the productscorresponding to all the test recording powers included in the thirdtest recording power group, and calculates a third gradient of the thirdstraight line; regarding the second value, selects at least two testrecording powers which are not completely the same as the at least twotest recording powers included in the third test recording power group,from the plurality of test recording powers, and sets a fourth testrecording power group including the selected at least two test recordingpowers; creates a fourth straight line based on all the test recordingpowers included in the fourth test recording power group and theproducts corresponding to all the test recording powers included in thefourth test recording power group, and calculates a fourth gradient ofthe fourth straight line; obtains a second ratio corresponding to thesecond value based on the third gradient and the fourth gradient; andcompares the first ratio and the second ratio, so as to determine one ofthe first value and the second value which corresponds to the higherlinearity.

In one embodiment, the calculation section, when setting the first testrecording power group, selects two largest test recording powers amongthe plurality of test recording powers; when setting the second testrecording power group, selects two smallest test recording powers amongthe plurality of test recording powers; when setting the third testrecording power group, selects two largest test recording powers amongthe plurality of test recording powers; and when setting the fourth testrecording power group, selects two smallest test recording powers amongthe plurality of test recording powers.

In one embodiment, the calculation section calculates a first averagepower indicating an average of all the plurality of test recordingpowers regarding the first value; calculates a second average powerindicating an average of all the plurality of test recording powersregarding the second value; when setting the first test recording powergroup, selects the test recording powers to be included in the firsttest recording power group from the plurality of test recording powers,such that an average of the test recording powers included in the firsttest recording power group is larger than the first average power; whensetting the second test recording power group, selects the testrecording powers to be included in the second test recording power groupfrom the plurality of test recording powers, such that an average of thetest recording powers included in the second test recording power groupis smaller than the first average power; when setting the third testrecording power group, selects the test recording powers to be includedin the third test recording power group from the plurality of testrecording powers, such that an average of the test recording powersincluded in the third test recording power group is larger than thesecond average power; and when setting the fourth test recording powergroup, selects the test recording powers to be included in the fourthtest recording power group from the plurality of test recording powers,such that an average of the test recording powers included in the fourthtest recording power group is smaller than the second average power.

In one embodiment, the output section outputs a signal to the recordingsection such that the recording section records the one of the pluralityof values which corresponds to the highest linearity on the informationstorage medium.

An information recording apparatus according to the present inventioncomprises a recording section for recording data on an informationstorage medium using an optical beam; a reading section for reading thedata recorded on the information storage medium; and a recording powerdetermination device for determining a recording power of the opticalbeam used when the recording section records the data on the informationstorage medium. The recording section records test data on theinformation storage medium at a plurality of test recording powers; thereading section reads the test data recorded on the information storagemedium at each of the plurality of test recording powers, generates asignal, and measures a modulation factor of the signal corresponding toeach of the plurality of test recording powers; and the recording powerdetermination device calculates a product of an n'th power of each ofthe plurality of test recording powers and the modulation factorcorresponding thereto, so as to obtain a plurality of productscorresponding to the plurality of test recording powers, calculates afirst recording power based on the correlation between the plurality oftest recording powers and the plurality of products, and calculates therecording power based on the first recording power, where n is a valueof exponent and is a real number other than 1.

In one embodiment, the value of exponent n is 2; the information storagemedium has a value of Pind, a value of ρ, and a value of κ recordedthereon; the reading section reads the value of Pind, the value of ρ,and the value of κ; the recording power determination device determinesa range of the plurality of test recording powers to be a range of 0.9times to 1.1 times the value of Pind; and the recording powerdetermination device creates an approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products, calculates the first recording power at which theproduct is 0 on the approximate line, and calculates a product of thefirst recording power, (−1/(the value of κ)+2) and the value of ρ.

In one embodiment, the recording section records the test data such thatthe signal generated by the reading section includes a plurality ofsingle cycle signals.

In one embodiment, the recording section forms a plurality of marks anda plurality of spaces on the information storage medium by the opticalbeam which has been modulated; and the recording section forms theplurality of marks such that an amplitude of the signal generated by thereading section is substantially the same as the amplitude of thelongest mark among the plurality of marks formed on the informationstorage medium.

In one embodiment, the recording power determination device obtains aplurality of products corresponding to the plurality of test recordingpowers regarding each of a plurality of values provided as the value ofexponent n, calculates a linearity of the correlation between theplurality of test recording power and the plurality of productsregarding each of the plurality of values, so as to calculate aplurality of linearities corresponding to the plurality of values, anddetermines one of the plurality of values which corresponds to thehighest linearity; and the recording section records one of theplurality of values which corresponds to the highest linearity on therecording information medium.

In one embodiment, the recording power determination device includes amemory for storing the one of a plurality of values which corresponds tothe highest linearity.

In one embodiment, the information storage medium has identificationinformation recorded thereon for identifying the information storagemedium; the reading section reads the identification information; thememory includes an identification information storage section forstoring the identification information and the one of the plurality ofvalues which corresponds to the highest linearity and corresponds to theidentification information; the identification information, and the oneof the plurality of values which corresponds to the highest linearityand corresponds to the identification information, are stored in theidentification information storage section; and the recording powerdetermination device reads the identification information recorded onthe information storage medium, determines whether or not the readidentification information is the same as the identification informationstored in the identification information storage section, and when theread identification information is determined to be the same as theidentification information stored in the identification informationstorage section, uses the value corresponding to the identificationinformation stored in the identification information storage section.

In one embodiment, the identification information includes dataindicating a manufacturer or a lot of the information storage medium.

An information storage medium according to the present inventionincludes an area for storing a value of exponent n corresponding to alinearity which is highest among a plurality of linearities, wherein thehighest linearity is obtained by: calculating a product of an n'th powerof each of a plurality of test recording powers and a modulation factorcorresponding thereto, thereby obtaining a plurality of productscorresponding to the plurality of test recording powers, and obtaining alinearity of the correlation between the plurality of test recordingpowers and the plurality of the products regarding each of a pluralityof values of exponent n, based on the plurality of test recording powersand the plurality of products corresponding to the plurality of testrecording powers.

A recording power determination method according to the presentinvention, for determining a recording power of an optical beam forrecording data on an information storage medium, wherein the informationstorage medium has a value of Mind and a value of ρ recorded thereon,comprises a value reading step of reading: a value recorded on theinformation storage medium, including the step of reading the value ofMind and the value of ρ; a confirming step of recording test data on theinformation storage medium at a plurality of test recording powers,reading the test data recorded at each of the plurality of testrecording powers, generating a signal, measuring a plurality ofmodulation factors of the signal corresponding to the plurality of testrecording powers, and confirming that largest modulation factor amongthe plurality of modulation factors is larger than the value of Mind andthat the smallest modulation factor among the plurality of modulationfactors is smaller than the value of Mind; a first recording powercalculating step of calculating a first recording power based on theplurality of test recording powers and the plurality of modulationfactors; and a recording power calculating step of calculating therecording power based on the first recording power and the value of ρ.

In one embodiment, the confirming step includes the steps of determiningwhether or not the largest modulation factor among the plurality ofmodulation factors is smaller than the value of Mind, and when thelargest modulation factor among the plurality of modulation factors isdetermined to be smaller than the value of Mind, repetitively recordingthe test data at a plurality of larger test recording powers until amodulation factor which is larger than the value of Mind is measured;and determining whether or not the smallest modulation factor among theplurality of modulation factors is larger than the value of Mind, andwhen the smallest modulation factor among the plurality of modulationfactors is determined to be larger than the value of Mind, repetitivelyrecording the test data at a plurality of smaller test recording powersuntil a modulation factor which is smaller than the value of Mind ismeasured.

In one embodiment, the first recording power calculating step includesthe steps of calculating a product of an n'th power of each of theplurality of test recording powers and a modulation factor correspondingthereto, thereby obtaining a plurality of products corresponding to theplurality of test recording powers, where n is a value of exponent andis a real number; and calculating the first recording power based on thecorrelation between the plurality of test recording powers and theplurality of products.

In one embodiment, the first recording power calculating step includesthe step of creating an approximate line indicating the correlationbetween the plurality of test recording powers and the plurality ofproducts, and calculating the first recording power at which the productis 0 on the approximate line.

In one embodiment, the value of exponent n is 1.

In one embodiment, the information storage medium has a value of Pindand a value of κ recorded thereon; the value reading step includes thestep of reading the value of Pind and the value of κ; the confirmingstep includes the step of setting a range of the plurality of testrecording powers to be a range of 0.9 times to 1.1 times the value ofPind; the first recording power calculating step includes the step ofcreating, an approximate line indicating the correlation between theplurality of test recording powers and the plurality of products, andcalculating the first recording power at which; the product is 0 on theapproximate line; and the recording power calculating step includes thestep of calculating a product of the first recording power, the value ofκ and the value of ρ.

In one embodiment, the value of exponent n is 2.

In one embodiment, the information storage medium has a value of Pindand a value of κ recorded thereon; the value reading step includes thestep of reading the value of Pind and the value of κ; the confirmingstep includes the step of setting a range of the plurality of testrecording powers to be a range of 0.9 times to 1.1 times the value ofPind; the first recording power calculating step includes the step ofcreating an approximate line indicating the correlation between theplurality of test recording powers and the plurality of products, andcalculating the first recording power at which the product is 0 on theapproximate line; and the recording power calculating step includes thestep of calculating a product of the first recording power, (−1/(thevalue of κ)+2) and the value of ρ.

In one embodiment, the confirming step includes the steps of calculatinga predetermined recording power at which the modulation factor is thevalue of Mind; and setting a range of the plurality of test recordingpowers such that the smallest test recording power among the pluralityof test recording powers is larger than 0.9 times the predeterminedrecording power.

In one embodiment, the confirming step includes the steps of calculatinga predetermined recording power at which the modulation factor is thevalue of Mind; and setting a range of the plurality of test recordingpowers such that the largest test recording power among the plurality oftest recording powers is smaller than 1.1 times the predeterminedrecording power.

In one embodiment, the confirming step includes the step of recordingthe test data such that the generated signal includes a plurality ofsingle cycle signals.

In one embodiment, the information storage medium has a plurality ofmarks and a plurality of spaces formed by the optical beam which hasbeen modulated; and the confirming step includes the step of forming theplurality of marks such that an amplitude of the generated signal issubstantially the same as the amplitude of the longest mark among theplurality of marks formed on the information storage medium.

In one embodiment, the information storage medium has a plurality oftracks concentrically or spirally formed therein.

A program according to the present invention causes an informationrecording apparatus to perform the steps of the above-describedrecording power determination method.

A recording power determination device according to the presentinvention, for determining a recording power of an optical beam usedwhen a recording section records data on an information storage medium,comprises an input section for receiving a signal indicating a pluralityof modulation factors corresponding to a plurality of test recordingpowers, a value of Mind, and a value of ρ; a calculation section forconfirming that the largest modulation factor among the plurality ofmodulation factors is larger than the value of Mind and that thesmallest modulation factor among the plurality of modulation factors issmaller than the value of Mind, calculating a first recording powerbased on the plurality of test recording powers and the plurality ofmodulation factors, and calculating the recording power based on thefirst recording power and the value of ρ; and an output section foroutputting a signal indicating the recording power calculated by thecalculation section to the recording section.

In one embodiment, the calculation section calculates a product of ann'th power of each of the plurality of test recording powers and amodulation factor corresponding thereto, so as to obtain a plurality ofproducts corresponding to the plurality of test recording powers, wheren is a value of exponent and is a real number; calculates the firstrecording power based on the correlation between the plurality of testrecording powers and the plurality of products; and calculates a productof the first recording power and the value of ρ.

In one embodiment, the calculation section creates an approximate lineindicating the correlation between the plurality of test recordingpowers and the plurality of products, and calculates the first recordingpower at which the product is 0 on the approximate line.

In one embodiment, the value of exponent n is 1; the input sectionreceives a value of Pind and a value of κ; the output section outputs asignal indicating the test recording powers in a range of 0.9 times to1.1 times the value of Pind to the recording section; and thecalculation section creates an approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products, calculates the first recording power at which theproduct is 0 on the approximate line, and calculates a product of thefirst recording power, the value of κ and the value of ρ.

In one embodiment, the value of exponent n is 2; the input sectionreceives a value of Pind and a value of κ; the output section outputs asignal indicating the test recording powers in a range of 0.9 times to1.1 times the value of Pind to the recording section; and thecalculation section creates an approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products, calculates the first recording power at which theproduct is 0 on the approximate line, and calculates a product of thefirst recording power, (−1/(the value of κ)+2) and the value of ρ.

In one embodiment, the calculation section calculates a predeterminedrecording power at which the modulation factor is the value of Mind, andsets the plurality of test recording powers such that the smallest testrecording power among the plurality of test recording powers is largerthan 0.9 times the predetermined recording power; and the output sectionoutputs a signal indicating the set plurality of test recording powersto the recording section.

In one embodiment, the calculation section calculates a predeterminedrecording power at which the modulation factor is the value of Mind, andsets the plurality of test recording powers such that the largest testrecording power among the plurality of test recording powers is smallerthan 1.1 times the predetermined recording power; and the output sectionoutputs a signal indicating the set plurality of test recording powersto the recording section.

An information recording apparatus according to the present inventioncomprises a recording section for recording data on an informationstorage medium using an optical beam; a reading section for reading thedata recorded on the information storage medium; and a recording powerdetermination device for determining a recording power of the opticalbeam used when the recording section records the data on the informationstorage medium. The information storage medium has a value of Mind and avalue of ρ recorded thereon; the reading section reads the value of Mindand the value of ρ; the recording section records test data on theinformation storage medium at a plurality of test recording powers; thereading section reads the test data recorded on the information storagemedium at each of the plurality of test recording powers, generates asignal, and measures a plurality of modulation factors of the signalcorresponding to the plurality of test recording powers; and therecording power determination device confirms that largest modulationfactor among the plurality of modulation factors is larger than thevalue of Mind and that the smallest modulation factor among theplurality of modulation factors is smaller than the value of Mind,calculates a first recording power based on the plurality of testrecording powers and the plurality of modulation factors, and calculatesthe recording power based on the first recording power and the value ofρ.

In one embodiment, the recording power determination device determineswhether or not the largest modulation factor among the plurality ofmodulation factors is smaller than the value of Mind, and when thelargest modulation factor among the plurality of modulation factors isdetermined to be smaller than the value of Mind, determines a pluralityof larger test recording powers until the reading section measures amodulation factor which is larger than the value of Mind; and therecording power determination device determines whether or not thesmallest modulation factor among the plurality of modulation factors islarger than the value of Mind, and when the smallest modulation factoramong the plurality of modulation factors is determined to be largerthan the value of Mind, determines a plurality of smaller test recordingpowers until the reading section measures a modulation factor which issmaller than the value of Mind.

In one embodiment, the recording power determination device calculates aproduct of an n'th power of each of the plurality of test recordingpowers and a modulation factor corresponding thereto, so as to obtain aplurality of products corresponding to the plurality of test recordingpowers, where n is a value of exponent and is a real number; calculatesthe first recording power based on the correlation between the pluralityof test recording powers and the plurality of products; and calculates aproduct of the first recording power and the value of ρ.

In one embodiment, the value of exponent n is 1; the information storagemedium has a value of Pind and a value of κ recorded thereon; thereading section reads the value of Pind and the value of κ; and therecording power determination device determines a range of the pluralityof test recording powers to be a range of 0.9 times to 1.1 times thevalue of Pind, creates an approximate line indicating the correlationbetween the plurality of test recording powers and the plurality ofproducts, calculates the first recording power at which the product is 0on the approximate line, and calculates a product of the first recordingpower, the value of κ and the value of ρ.

In one embodiment, the value of exponent n is 2; the information storagemedium has a value of Pind and a value of κ recorded thereon; thereading section reads the value of Pind and the value of κ; therecording power determination device determines a range of the pluralityof test recording powers to be a range of 0.9 times to 1.1 times thevalue of Pind, creates an approximate line indicating the correlationbetween the plurality of test recording powers and the plurality ofproducts, calculates the first recording power at which the product is 0on the approximate line, and calculates a product of the first recordingpower, (−1/(the value of κ)+2) and the value of ρ.

In one embodiment, the recording power determination device calculates apredetermined recording power at which the modulation factor is thevalue of Mind, and determines a range of the plurality of test recordingpowers such that the smallest test recording power among the pluralityof test recording powers is larger than 0.9 times the predeterminedrecording power.

In one embodiment, the recording power determination device calculates apredetermined recording power at which the modulation factor is thevalue of Mind, and determines a range of the plurality of test recordingpowers such that the largest test recording power among the plurality oftest recording powers is smaller than 1.1 times the predeterminedrecording power.

In one embodiment, the recording section records the test data such thatthe signal generated by the reading section includes a plurality ofsingle cycle signals.

In one embodiment, the recording section forms a plurality of marks anda plurality of spaces on the information storage medium by the opticalbeam which has been modulated; and the recording section forms theplurality of marks such that an amplitude of the signal generated by thereading section is substantially the same as the amplitude of thelongest mark among the plurality of marks formed on the informationstorage medium.

According to a recording power determination method and a recordingpower determination device of the present invention, an appropriaterecording power can be determined, and thus data can be properlyrecorded. In addition, an information storage medium can be preventedfrom being deteriorated unnecessarily quickly.

According to a program of the present invention, an appropriaterecording power can be determined, and thus data can be properlyrecorded. In addition, an information storage medium can be preventedfrom being deteriorated unnecessarily quickly.

According to an information recording apparatus of the presentinvention, an appropriate recording power can be determined, and thusdata can be properly recorded. In addition, an information storagemedium can be prevented from being deteriorated unnecessarily quickly.

According to an information recording apparatus of the presentinvention, a value corresponding to the highest linearity among aplurality of values each recorded on an information storage medium asthe value of exponent is read. Using the value, an appropriate recordingpower can be determined quickly with no need of comparison on linearity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an optical disc in the presentinvention.

FIG. 2 is a schematic view showing an embodiment of an optical discapparatus according to the present invention.

FIG. 3 is a schematic view for describing the relationship between abinary signal waveform and a pulse waveform for forming marks in thepresent invention.

FIG. 4 is a schematic view showing an embodiment of a reproductionsection of an optical disc apparatus according to the present invention.

FIG. 5 is a schematic view showing an embodiment of a recording powerdetermination device of an optical disc apparatus according to thepresent invention.

FIG. 6 is a flowchart for describing a first embodiment of a recordingpower determination method according to the present invention.

FIG. 7 is a schematic view for describing test data recording performedon an optical disc at a plurality of test recording powers by the firstembodiment of the recording power determination method according to thepresent invention.

FIG. 8 shows a view for describing the first embodiment of the recordingpower determination method according to the present invention, in whichFIG. 8( a) is a graph illustrating the relationship between the testrecording power and the modulation factor, and FIG. 8( b) is a graphillustrating the relationship between (i) the test recording power and(ii) the product of the modulation factor and the square of the testrecording power.

FIG. 9 shows a view for describing an influence of a tilt in the firstembodiment of the recording power determination method according to thepresent invention, in which FIG. 9( a) is a graph illustrating therelationship between the recording power and the modulation factor, andFIG. 9( b) is a graph illustrating the relationship between (i) therecording power and (ii) the product of the modulation factor and thesquare of the recording power.

FIG. 10 shows a view for describing the first embodiment of therecording power determination method according to the present inventionand is a graph illustrating the relationship between the test recordingpower and the modulation factor.

FIG. 11 shows a view for describing the first embodiment of therecording power determination method according to the present inventionand is a graph illustrating the relationship between (i) the testrecording power and (ii) the product of the modulation factor and thetest recording power.

FIG. 12 shows a view for describing an influence of a tilt in a secondembodiment of a recording power determination method according to thepresent invention, in which FIG. 12( a) is a graph illustrating therelationship between the test recording power and the modulation factor,FIG. 12( b) is a graph illustrating the relationship between (i) thetest recording power and (ii) the product of the modulation factor andthe square of the test recording power, and FIG. 12( c) is a graphillustrating the relationship between (i) the test recording power and(ii) the product of the modulation factor and the cube of the testrecording power.

FIG. 13 is a flowchart for describing a third embodiment of a recordingpower determination method according to the present invention.

FIG. 14 shows a view for describing the third embodiment of therecording power determination method according to the present invention,in which FIG. 14( a) is a graph illustrating the relationship betweenthe test recording power and the modulation factor, and FIG. 14( b) is agraph illustrating the relationship between (i) the test recording powerand (ii) the product of the modulation factor and the square of the testrecording power.

FIG. 15 shows a view for describing a fourth embodiment of a recordingpower determination method according to the present invention, in whichFIG. 15( a) is a graph illustrating the relationship between the testrecording power and the modulation factor, and FIG. 15( b) is a graphillustrating the relationship between (i) the test recording power and(ii) the product of the modulation factor and the test recording power.

FIG. 16 is a schematic view showing a general optical disc.

FIG. 17 is a schematic view showing a conventional optical discapparatus.

FIG. 18 is a schematic view showing a reproduction section of theconventional optical disc apparatus.

FIG. 19 is a schematic view for describing a modulation factor.

FIG. 20 is a schematic view for describing test data recording performedon an optical disc at a plurality of test recording powers by aconventional recording power determination method.

FIG. 21 shows a view for describing a first conventional recording powerdetermination method and is a graph illustrating the relationshipbetween the test recording power and the modulation factor.

FIG. 22 shows a view for describing a second conventional recordingpower determination method and is a graph illustrating the relationshipbetween (i) the test recording power and (ii) the product of themodulation factor and the test recording power.

FIG. 23 shows a view for describing an influence of a tilt according tothe first conventional recording power determination method and is agraph illustrating the relationship between the recording power and themodulation factor.

FIG. 24 shows a view for describing the second conventional recordingpower determination method and is a graph illustrating the relationshipbetween (i) the test recording power and (ii) the product of themodulation factor and the test recording power.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Embodiment 1

Hereinafter, Embodiment 1 of a recording power determination method anda recording power determination device according to the presentinvention will be described with reference to FIGS. 1 through 11.

FIG. 1 is a schematic view showing an optical disc 101 in thisembodiment. The optical disc 101 has a track 301 formed thereinspirally. By irradiating the track 301 with an optical beam having amodified recording power, a plurality of marks and a plurality of spacesare formed on the track 301. Thus, data is recorded. The optical disc101 includes a user data area used for data recording by the user and arecording power determination area used for determining a recordingpower of the optical beam. The recording power determination area isprovided in an area other than the user data area (specifically, aninnermost area or an outermost area of the optical disc 101).

FIG. 2 is a schematic view showing an optical disc apparatus 100including a recording power determination device 108 of this embodiment.The optical disc apparatus 100 includes a recording section 210 forrecording data on the optical disc 101 using an optical beam, a readingsection 220 for reading data recorded on the optical disc 101, arecording power determination device 108 for determining a recordingpower of the optical beam used when the recording section 210 recordsdata on the optical disc 101, and a demodulation/ECC (Error CorrectingCode) circuit 106. The recording section 210 includes an optical head102, a recording power setting section 110, a laser driving circuit 112,and a recording data generation section 114. The reading section 220includes the optical head 102 and a reproduction section 104.

When the optical disc 101 is mounted on the optical disc apparatus 100,the type of the optical disc 101 is identified, and the optical disc 101is rotated. The optical head 102 has a semiconductor laser (not shown).While being rotated, the optical disc 101 is irradiated with an opticalbeam emitted from the semiconductor laser of the optical head 102.

For recording data on the optical disc 101, the optical head 102irradiates the optical disc 101 with an optical beam having apredetermined recording power to form marks on the optical disc 101. Inthis example, data of the Run Length Limited (1,7) modulation system isrecorded by a mark edge recording method. In this case, seven types ofmarks and spaces are formed on the optical disc 101 on the basis ofreference cycle T, which is 2T at the shortest and 8T at the longest.

For reading data from the optical disc 101, the optical head 102irradiates the optical disc 101 with an optical beam having areproduction power which is smaller than the recording power andreceives light reflected by the optical disc 101. The optical head 102performs optical/electric conversion on the received light to generate asignal indicating the data recorded on the optical disc 101.

FIG. 3 shows a schematic view for describing the relationship between abinary signal waveform and a pulse waveform for forming marks. FIG. 3shows a binary signal waveform corresponding to a 2T mark and a pulsewaveform for forming the 2T mark, a binary signal waveform correspondingto a 3T mark and a pulse waveform for forming the 3T mark, and a binarysignal waveform corresponding to a 4T mark and a pulse waveform forforming the 4T mark.

The parameters of the recording power are peak power (Pp), bias power(Pe), and bottom power (Pbw). In this embodiment, the ratio among thepeak power, the bias power, and the bottom power is constant. As shownin FIG. 3, the number of pulses indicating Pp is one for a 2T mark andtwo for a 3T mark, and increases one by one as the mark length isincreased one T by one T.

The time-related parameters of the pulse waveform are Ttop, dTtop, Tmpand dTe. In FIG. 3, Ttop represents the time length in which the firstpulse indicates Pp, and dTop represents the time length between time 1Tafter the rise of the binary signal waveform and the time of rise of thefirst pulse. Tmp represents the time length in which the pulses otherthan the first pulse indicates Pp, and dTe represents the time lengthbetween the time of fall of the binary signal waveform and the time atwhich the last pulse rises from Pbw to Pe.

In this embodiment, the peak power (Pp), the bias power (Pe), the bottompower (Pbw) are common among all the marks (2T through 8T). Tmp is alsocommon among all the marks. Ttop, dTtop and dTe are set as beingclassified into three classes of 2T, 3T, and 4T or greater.

Returning to FIG. 2, the reproduction section 104 of the optical discapparatus 100 measures the modulation factor of the signal generated bythe optical head 102 and digitizes the signal generated by the opticalhead 102. The demodulation/ECC circuit 106 demodulates the signaldigitized by the reproduction section 104 and corrects errors. Therecording power determination device 108 determines the recording powerfor recording data based on the modulation factor measured by thereproduction section 104. The recording power setting section 110 setsthe recording power determined by the recording power determinationdevice 108 in the laser driving circuit 112. The recording datageneration section 114 generates data to be recorded on the optical disc101. The laser driving circuit 112 drives the optical head 102 to recordthe data generated by the recording data generation section 114 on theoptical disc 101 at the recording power set by the recording powersetting section 110.

FIG. 4 is a schematic view showing the reproduction section 104 in theoptical disc apparatus 100 of this embodiment. As shown in FIG. 4, thereproduction section 104 includes a preamplifier 201, a sampling andholding circuit 202, an A/D converter 203, an arithmetic operator 204,and a binary data generation section 205.

The binary data generation section 205 digitizes the signal generated bythe optical head 102 to generate digitized data (binary data), andoutputs a signal 105 indicating the binary data to the demodulation/ECCcircuit 106 and the recording power determination device 108.

The preamplifier 201 amplifiers the signal generated by the optical head102. The sampling and holding circuit 202 samples the signal amplifiedby the preamplifier 201 and holds the peak value and the bottom value ofthe signal. The A/D converter 203 digitizes the peak value and thebottom value held by the sampling and holding circuit 202. Thearithmetic operator 204 performs an arithmetic operation on thedigitized peak value and bottom value to obtain a modulation factor, andoutputs a signal 107 indicating the modulation factor to the recordingpower determination device 108.

FIG. 5 is a schematic view showing the recording power determinationdevice 108 of this embodiment. As shown in FIG. 5, the recording powerdetermination device 108 includes an input section 401 for receiving thesignal 107 indicating the modulation factor, a calculation section 402for calculating the recording power of the optical beam used when therecording section 210 records data on the optical disc 101, an outputsection 403 for outputting the calculated recording power to therecording power setting section 110 of the recording section 210, and amemory 404.

Hereinafter, a recording power determination method of this embodimentwill be described with reference to FIG. 6.

On the optical disc 101, a constant parameter is recorded to be used fordetermination of the recording power. As shown in S12 of FIG. 6, theoptical head 102 generates a signal 103 indicating the constantparameter (hereinafter, referred to as a “predetermined value”) readfrom the optical disc 101, and outputs the signal 103 to thereproduction section 104. The binary data generation section 205 of thereproduction section 104 generates the binary signal 105 obtained bybinarizing the signal 103 indicating the predetermined value, andoutputs the signal 105 to the recording power determination device 108.

As shown in S14 of FIG. 6, test data is recorded on the optical disc 101at a plurality of test recording powers. For recording the test data,the recording power determination device 108 outputs a signal 109indicating predetermined eight different test recording powers A throughH to the recording power setting section 110. The recording powersetting section 110 sets the test recording powers A through H in thelaser driving circuit 112. In this example, the test recording power Ais the largest power, and the test recording powers become smaller fromthe test recording power B toward the test recording power H.

The recording data generation section 114 generates test data, andoutputs a signal 115 indicating the generated test data to the laserdriving circuit 112. The laser driving circuit 112 drives the opticalhead 102 to record the test data over substantially one circle of thetrack continuously from a predetermined position in the recording powerdetermination area of the optical disc 101. The recording datageneration section 114 generates the test data such that the opticalhead 102 continuously forms 8T marks and 8T spaces on the optical disc101. The test data is repeatedly recorded over substantially one circleof the optical disc 101 at the test recording powers A through H. FIG. 7shows areas of the optical disc 101 corresponding to the test recordingpowers A through H with letters “A” through “H”. By recording the dataover substantially one circle of the optical disc 101 a plurality oftimes repeatedly, the influence of tilts dispersed in thecircumferential direction of the optical disc 101 can be removed.

Returning to FIG. 6, when the recording of the test data is finished, asshown in S16 of FIG. 6, the optical head 102 irradiates the optical disc101 with an optical beam having a reproduction power. By this, the testdata recorded on the track of the optical disc 101 is read, and a signalindicating the test data is generated. The amplitude of the signalgenerated by the optical head 102 changes in accordance with whether ornot the marks are formed on the optical disc 101. The signal 103generated by the optical head 102 is input to the reproduction section104.

As shown in FIG. 3, the preamplifier 201 of the reproduction section 104amplifies the signal 103. The sampling and holding circuit 202 holds thepeak value and the bottom value of the signal amplified by thepreamplifier 201. The A/D converter 203 digitizes the peak value and thebottom value of the signal held by the sampling and holding circuit 202.The arithmetic operator 204 performs an arithmetic operation on thedigitized peak value and bottom value to obtain a modulation factor ofthe signal. Since the amplitude of the signal 703 is different inaccordance with the test recording powers A through H, the modulationfactor is also different in accordance with the test recording powers Athrough H. The arithmetic operator 204 generates a signal 107 indicatingthe modulation factor of the signal, and outputs the signal 107 to therecording power determination device 108.

As shown in FIG. 5, the signal 107 indicating the modulation factorcorresponding to each of the test recording powers A through H is inputto the input section 401 of the recording power determination device 108from the arithmetic operator 204 of the reproduction section 104.

As shown in S18 of FIG. 6, the calculation section 402 of the recordingpower determination device 108 calculates a product of the modulationfactor corresponding to the test recording power A and the square of thetest recording power A. The calculation section 402 also calculates aproduct of the modulation factor corresponding to each of the testrecording powers B through H and the square of each of the testrecording powers B through H. Thus, the calculation section 402 obtainsa plurality of products corresponding to the test recording powers Athrough H.

Next, as shown in S20 of FIG. 6, the calculation section 402 calculatesa first recording power based on the correlation between the pluralityof test recording powers A through H and the plurality of products.Specifically, the calculation section 402 creates an approximate lineindicating the correlation between the plurality of test recordingpowers and the plurality of products, and sets the recording power atwhich the product is 0 on the approximate line as the first recordingpower. Hereinafter, this will be described in detail with reference toFIG. 8.

FIG. 8( a) is a graph illustrating the relationship between the testrecording power and the modulation factor corresponding to the testrecording power. FIG. 8( b) is a graph illustrating the relationshipbetween (i) the test recording power and (ii) the product of themodulation factor and the square of the test recording power. As isclear from FIGS. 8( a) and 8(b), the linearly of the correlation betweenthe test recording power and the modulation factor is low, whereas thelinearly of the correlation between (i) the test recording power and(ii) the product of the modulation factor and the square of the testrecording power is high. In the graph of FIG. 8( b), the eight pointscorresponding to the test recording powers A through H are arrangedsubstantially on a straight line.

The calculation section 402 calculates a recording power P500 at whichthe product of the modulation factor and the square of the testrecording power is 0 on the approximate line shown in the graph of FIG.8( b).

Next, as shown in S22 of FIG. 6, the calculation section 402 calculatesthe recording power based on the recording power P500. Specifically, thecalculation section 402 performs an arithmetic operation on therecording power P500 and a predetermined value recorded on the opticaldisc 101, so as to calculate the recording power.

The output section 403 outputs a signal 109 indicating the recordingpower calculated by the calculation section 402 to the recording powersetting section 110.

A program may be used such that a CPU (not shown) controls the elementsof the optical disc apparatus 100 in the above-described procedure. Theprogram may be stored on a computer-readable recording medium (notshown), such as an EEPROM, ROM, RAM, hard disc, magnetic recordingmedium or the like.

Next, with reference to FIG. 9, the relationship between the recordingpower and the modulation factor in the case where there is a relativetilt between the optical disc 101 and the optical head 102 will bedescribed.

FIG. 9( a) is a graph illustrating the relationship between therecording power and the modulation factor corresponding to the recordingpower, and is similar to FIG. 23. In the graph of FIG. 9( a), a solidline 1201A represents the result obtained when there is no tilt at thetime of data recording or at the time of reading of the recorded data. Asolid line 1202A represents the result obtained when there is a tilt atthe time of data recording, but there is no tilt at the time of datareading. A solid line 1203A represents the result obtained when there isa tilt both at the time of data recording and at the time of datareading. The modulation factor is smaller when there is a tilt than whenthere is no tilt. In the case where there is no tilt at the time of datareading but there is a tilt at the time of data recording, themodulation factor corresponding to the test recording power H, which issmallest among the eight test recording powers, cannot be measured.Similarly, in the case where there is a tilt both at the time of datarecording and at the time of data reading, the modulation factorcorresponding to the test recording power H cannot be measured.

FIG. 9( b) is a graph illustrating the relationship between (i) therecording power shown in FIG. 9( a) and (ii) the product of themodulation factor shown in FIG. 9( a) and the square of the recordingpower. In the graph of FIG. 9( b), a solid line 1201B represents theresult obtained when there is no tilt at the time of data recording orat the time of reading of the recorded data. A solid line 1202Brepresents the result obtained when there is a tilt at the time of datarecording, but there is no tilt at the time of data reading. A solidline 1203B represents the result obtained when there is a tilt both atthe time of data recording and at the time of data reading.

As described above, test data is recorded and read before user data isrecorded. The test data is read immediately after being recorded.Accordingly, when the test data is recorded and read while there is arelative tilt, the results represented by the solid lines 1203A and1203B are obtained.

According to this embodiment, as shown in FIG. 9( b), the recordingpower determination device 108 calculates a recording power P1203 atwhich the product of the modulation factor and the square of the testrecording power is 0, calculates the recording power based on therecording power P1203 and a predetermined value recorded on the opticaldisc 101, and outputs a signal 109 indicating the calculated recordingpower to the recording power setting section 110.

The result represented by the solid line 1203B is influenced by the tiltat the time of recording and also by the tilt at the time of reading. Asdescribed above, only the influence of the tilt at the time of recordingneeds to be considered for determining the recording power. Therefore,the recording power to be selected at this point is essentially therecording power P1202, but the recording power P1203 selected by therecording power determination method of this embodiment isexperimentally confirmed to be generally equal to the recording powerP1202 to be selected, as shown in FIG. 9( b).

Namely, the recording power at which the product of the modulationfactor and the square of the recording power is 0 is a criticalrecording power necessary for forming marks on the optical disc 101.When a recording power larger than the critical recording power is used,a modulation factor which is not 0 is measured regardless of whetherthere is a tilt or not at the time of reading. Therefore, the recordingpower at which the product of the modulation factor and the square ofthe recording power is 0 is the same regardless of whether there is atilt or not at the time of reading.

As described above, according to this embodiment, even where there is arelative tilt between the optical disc and the optical head, anappropriate recording power can be determined and thus data can beproperly recorded. According to this embodiment, the optical disc isprevented from being deteriorated unnecessarily quickly by repeatedrecording.

According to this embodiment, an appropriate recording power can bedetermined against any stress which deteriorates the modulation factorboth at the time of recording and at the time of reproduction, notlimited to against a tilt.

This embodiment is especially effective in an optical disc apparatusconformed to the BD (Blu-ray Disc) format which requires more preciserecording power control for higher density recording.

Disc manufacturers which manufacture optical discs conformed to the BDformat determine in advance the recording power Pwo which is recommendedfor data recording on an optical disc before shipping the optical discs.The recording power Pwo is determined such that when an ideal opticaldisc apparatus records data on an ideal optical disc at the recordingpower Pwo and then reads the data, an appropriate modulation factor ismeasured. However, due to the individual differences among actualoptical discs and optical disc apparatuses, even when an optical discapparatus records data at the recording power Pwo, an appropriatemodulation factor is not necessarily measured when the data is read.

Accordingly, for recording data on an optical disc, an optical discapparatus determines an appropriate recording power after checking therelationship between each of a plurality of test recording powers and amodulation factor corresponding thereto. The disc manufacturerspre-store constant parameters used for determining an appropriaterecording power on the optical disc. The constant parameters are Pind,ρ, κ, and Mind. Although these will be described later in detail, anappropriate recording power for recording data on an optical disc isobtained using a recording power Pind which is smaller than therecording power Pwo, and the relationship between the recording powerPind and a modulation factor Mind. It is not recommended to directlydetermine the recording power Pwo for the following reasons: (1) sincethe modulation factor saturates in the vicinity of the recording powerPwo, it is difficult to detect a change in the optimum recording powercaused by an external disturbance such as a tilt or the like asdescribed above with reference to FIG. 9; and (2) the repeateddetermination of the recording power results in the deterioration of theoptical disc 101.

Hereinafter, with reference to FIGS. 10 and 11, the relationship amongthe recording power Pwo recommended by the optical disc manufactures,Pind, ρ, κ, and Mind will be described.

The disc manufacturers determine the recording power Pwo, then determinethe recording power Pind, and determine ρ based on the relationship ofρ=recording power Pwo/recording power Pind.

As shown in FIG. 10, the disc manufacturers read data recorded at therecording power Pind so as to form 8T marks and set the modificationfactor of the signal corresponding to the data as the modificationfactor Mind.

As shown in FIG. 11, the disc manufacturers read test data recorded at aplurality of test recording powers within a range of 0.9 times to 1.1times the recording power Pind so as to form 8T marks, generate asignal, and measure a plurality of modulation factors of the signal. Theplurality of modulation factors respectively correspond to the pluralityof test recording powers.

The disc manufacturers calculate a product of each test recording powerand a modulation factor corresponding thereto, and calculate a recordingpower Pthr based on the correlation between the plurality of testrecording powers and the plurality of products. Specifically, anapproximate line indicating the correlation between the plurality oftest recording powers and the plurality of products is created, and therecording power at which the product is 0 on the approximate line is setas the recording power Pthr. Then, the value of κ is determined based onthe relationship of κ=recording power Pind/recording power Pthr.

The disc manufacturers pre-store the value of Pind, the value of ρ, thevalue of κ, and the value of Mind on the optical disc 101.

In this embodiment, a value corresponding to the recording power Pthr atwhich the modulation factor is 0 is calculated based on the relationshipbetween the test recording power and the modulation factor, therecording power (i.e., the value corresponding to Pind) is calculatedbase on the value of the recording power Pthr and the value of κ, andthe recording power Pw is calculated based on the value of thecalculated recording power and the value of ρ.

Hereinafter, a recording power determination method of this embodimentin the case where the optical disc is conformed to the BD format will bedescribed.

The reproduction section 104 reads the value of κ and the value of ρrecorded on the optical disc 101, and outputs a signal 105 indicatingthe value of κ and the value of ρ to the recording power determinationdevice 108.

After the recording section 210 of the optical disc apparatus 100records test data at the test recording powers A through H, thereproduction section 104 measures a plurality of the modulation factorscorresponding to the plurality of test recording powers. Thereproduction section 104 outputs a signal 107 indicating the pluralityof modulation factors corresponding to the plurality of test recordingpowers to the recording power determination device 108.

When the result as shown in FIG. 8( a) is obtained by reading the testdata, the recording power determination device 108 calculates arecording power P500 at which the product of the modulation factor andthe square of the recording power is 0 as shown in FIG. 8( b), andcalculates a recording power Pw1 for recording data in accordance withthe following expression 1.Pw1=P500×(−1/κ+2)×ρ  expression 1

The recording power determination device 108 outputs a signal 109indicating the calculated recording power Pw1 to the recording powersetting section 110.

As described above, according to this embodiment, since the linearity ofthe correlation between (i) the test recording power and (ii) theproduct of the modulation factor and the square of the test recordingpower is high, an appropriate recording power can be determined withoutrelying on the range of the test recording powers.

In the above description, the first recording power (P500) is calculatedusing the product of the modulation factor and the square of the testrecording power, i.e., the product in the case where the value ofexponent n of the test recording power is 2. The present invention isnot limited to this. Depending on the structure of the optical disc orthe characteristics of the recording film of the optical disc, thelinearity of the correlation between (i) the test recording power and(ii) the product of the modulation factor and the n'th power of the testrecording power may be high in the case where the value of exponent n isnot 2. Accordingly, the value of exponent n is not limited to 2.

It should be noted though that as described above with reference to FIG.22, such a linearity when the value of exponent is 1, i.e., thelinearity of the correlation between (i) the test recording power and(ii) the product of the modulation factor and the test recording power,is low. In the graph of FIG. 22, the plotted points are off the straightline.

Accordingly, the value of exponent n is any real number other than 1.Experiments were performed on the value of exponent n using severalexistent optical discs. When, for example, the value of exponent n is1.5 to 2.5, the linearity of the correlation between (i) the testrecording power and (ii) the product of the modulation factor and then'th power of the test recording power was high. However, the value ofexponent n is not limited to these values, and may be 0.5, 0 or −1, forexample.

According to this embodiment, the linearity of the correlation between(i) the test recording power and (ii) the product of the modulationfactor and the n'th power of the test recording power can be made high.Therefore, a recording power at which the product of the modulationfactor and the n'th power of the test recording power is 0 can becalculated regardless of the test recording power.

The appropriate recording power P500 can be obtained without recordingdata at eight test recording powers A through H as shown in FIG. 7. Theappropriate recording power P500 can be obtained by recording data atfour recording powers A through D, four recording powers E through H, orfour recording powers C through F. When determining a recording powerusing a predetermined width of area, the number of repetitions can beincreased and thus the precision of the recording power to be determinedcan be increased by decreasing the number of the test recording powers.

It is preferable that the value of exponent n is recorded on the opticaldisc 101. By recording the value of exponent n on the optical disc 101,the degree of freedom for designing the structure of the optical discapparatus 101 or the recording film in the optical disc 101 can beenhanced.

The recording power determination method of this embodiment isespecially effective in an optical disc apparatus required to controlthe recording power at higher precision for higher density recording,such as an optical disc apparatus conformed to the BD format.

Embodiment 2

Hereinafter, Embodiment 2 of a recording power determination method anda recording power determination device according to the presentinvention will be described with reference to FIG. 12.

A recording power determination device 108 of this embodiment hassubstantially the same structure as that of the recording powerdetermination device described in Embodiment 1 with reference to FIG. 5.An optical disc apparatus 100 including the recording powerdetermination device 108 of this embodiment also has substantially thesame structure as that of the optical disc apparatus described inEmbodiment 1 with reference to FIG. 2. In order to avoid redundancy, therecording power determination device 108 and the optical disc apparatus100 of this embodiment will not be described regarding the points whichare the same as those of Embodiment 1.

Unlike in Embodiment 1, the recording power determination device 108 ofthis embodiment calculates a product of the modulation factor and ann'th power of the test recording power regarding each of a plurality ofvalues of exponent n, calculates the linearity of the correlationbetween (i) the test recording power and (ii) the product of themodulation factor and the n'th power of the test recording power, anddetermines the recording power using one of the plurality of values ofexponent n which corresponds to the highest linearity.

Hereinafter, a recording power determination method when the values ofexponent n are 2 and 3 will be described with reference to FIGS. 2 and5.

The reproduction section 104 outputs a signal 107 indicating a pluralityof modulation factors corresponding to the plurality of test recordingpowers to the recording power determination device 108. The signal 107indicating the modulation factors corresponding to the test recordingpowers A through H is input to the input section 401 of the recordingpower determination device 108 from the arithmetic operator 204 of thereproduction section 104.

The calculation section 402 calculates a product of the modulationfactor corresponding to the test recording power A and the square of thetest recording power A. The calculation section 402 calculates a productof the modulation factor corresponding to each of the test recordingpowers B through H and the square of each of the test recording powers Bthrough H. Thus, the calculation section 402 obtains a plurality ofproducts corresponding to the test recording powers A through H in thecase where the value of exponent n is 2.

The calculation section 402 also calculates a product of the modulationfactor corresponding to the test recording power A and the cube of thetest recording power A. The calculation section 402 calculates a productof the modulation factor corresponding to each of the test recordingpowers B through H and the cube of each of the test recording powers Bthrough H. Thus, the calculation section 402 obtains a plurality ofproducts corresponding to the test recording powers A through H in thecase where the value of exponent n is 3.

FIG. 12( a) is a graph illustrating the relationship between the testrecording power and the modulation factor corresponding to the testrecording power. FIG. 12( b) is a graph illustrating the relationshipbetween (i) the test recording power and (ii) the product of themodulation factor and the square of the test recording power. FIG. 12(c) is a graph illustrating the relationship between (i) the testrecording power and (ii) the product of the modulation factor and thecube of the test recording power.

The calculation section 402 compares the linearity obtained when thevalue of exponent n is 2 and the linearity obtained when the value ofexponent n is 3, and determines which linearity is higher. Thecomparison on linearity will be described later. Here, when, forexample, the linearity obtained when the value of exponent n is 2 ishigher than the linearity obtained when the value of exponent n is 3,the calculation section 402 calculates a recording power P500 based onthe correlation between the plurality of test recording powers A throughH and the plurality of products corresponding thereto (calculated above)in the case where the value of exponential n is 2. Specifically, thecalculation section 402 creates an approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products, and calculates the recording power P500 at whichthe product is 0 on the approximate line. Then, the calculation section402 performs an arithmetic operation on the recording power P500 and apredetermined value read from the optical disc 101 so as to calculatethe recording power. The output section 403 outputs a signal 109indicating the calculated recording power to the recording power settingsection 110, and the recording power setting section 110 sets therecording power in the laser driving circuit 112.

With reference to FIGS. 12( b) and 12(c), the comparison on linearitywill be described.

When the value of exponent is 2, the calculation section 402 calculatesthe linearity of the correlation between (i) the test recording powerand (ii) the product of the modulation factor and the square of the testrecording power. For example, the calculation section 402 selects thelargest two among the test recording powers A through H (the testrecording powers A and B) and the smallest two among the test recordingpowers A through H (the test recording powers G and H). Referring to thegraph of FIG. 12( b), the calculation section 402 creates a straightline connecting the point corresponding to the test recording power Aand the point corresponding to the test recording power B (hereinafter,this straight line will be referred to as a “first straight line”), andcalculates the gradient of the first straight line (hereinafter,referred to as a “first gradient”). Also referring to the graph of FIG.12( b), the calculation section 402 creates a straight line connectingthe point corresponding to the test recording power G and the pointcorresponding to the test recording power H (hereinafter, this straightline will be referred to as a “second straight line”), and calculatesthe gradient of the second straight line (hereinafter, referred to as a“second gradient”). The calculation section 402 calculates the ratiobetween the first gradient and the second gradient (hereinafter, thisratio will be referred to as a “first ratio”).

When the value of exponent is 3 also, the calculation section 402calculates the linearity of the correlation between (i) the testrecording power and (ii) the product of the modulation factor and thecube of the test recording power. For example, the calculation section402 selects the largest two among the test recording powers A through H(the test recording powers A and B) and the smallest two among the testrecording powers A through H (the test recording powers G and H).Referring to the graph of FIG. 12( c), the calculation section 402creates a straight line connecting the point corresponding to the testrecording power A and the point corresponding to the test recordingpower B (hereinafter, this straight line will be referred to as a “thirdstraight line”), and calculates the gradient of the third straight line(hereinafter, referred to as a “third gradient”). Also referring to thegraph of FIG. 12( c), the calculation section 402 creates a straightline connecting the point corresponding to the test recording power Gand the point corresponding to the test recording power H (hereinafter,this straight line will be referred to as a “fourth straight line”), andcalculates the gradient of the fourth straight line (hereinafter,referred to as a “fourth gradient”). The calculation section 402calculates the ratio between the third gradient and the fourth gradient(hereinafter, this ratio will be referred to as a “second ratio”).

Then, the calculation section 402 compares the first ratio and thesecond ratio, and determines that a linearity of the value of exponentvalue corresponding to one of the first ratio and the second ratio,which is closer to ratio 1, is higher. Then, as described above, thecalculation section 402 calculates the recording power based on thecorrelation corresponding to the value of exponent value providing thehigher linearity. Since the calculation section 402 determines therecording power based on the correlation corresponding to the value ofexponent value providing the higher linearity, a more appropriaterecording power can be determined.

However, the method for comparison on linearity is not limited to this.In the above description, the calculation section 402 compares thegradient in the vicinity of the maximum value among the plurality oftest recording powers and the gradient in the vicinity of the minimumvalue among the plurality of test recording powers. The calculationsection 402 may use a different method as described below to compare thegradient in the vicinity of the maximum value and the gradient in thevicinity of the minimum value among the plurality of test recordingpowers.

When the value of exponent n is 2, the calculation section 402calculates a first average power, which indicates an average of all theplurality of test recording powers. Next, the calculation section 402selects at least two test recording powers as test recording powersbelonging to one group of test recording powers (hereinafter, referredto as a “first test recording power group”) from the plurality of testrecording powers. The test recording powers belonging to the first testrecording power group are selected such that an average of such testrecording powers is larger than the first average power. Then, thecalculation section 402 creates a first straight line indicating thecorrelation between the test recording powers belonging to the firsttest recording power group and the products corresponding to these testrecording powers, and calculates a first gradient of the first straightline. Further, the calculation section 402 selects at least two testrecording powers as test recording powers belonging to another group oftest recording powers (hereinafter, referred to as a “second testrecording power group”) from the plurality of test recording powers. Thetest recording powers belonging to the second test recording power groupare selected such that an average of such test recording powers issmaller than the first average power. Then, the calculation section 402creates a second straight line indicating the correlation between thetest recording powers belonging to the second test recording power groupand the products corresponding to these test recording powers, andcalculates a second gradient of the second straight line. Then, thecalculation section 402 calculates a first ratio based on the firstgradient and the second gradient.

When the value of exponent n is 3 also, the calculation section 402calculates a second average power, which indicates an average of all theplurality of test recording powers. Next, the calculation section 402selects at least two test recording powers as test recording powersbelonging to one group of test recording powers (hereinafter, referredto as a “third test recording power group”) from the plurality of testrecording powers. The test recording powers belonging to the third testrecording power group are selected such that an average of such testrecording powers is larger than the second average power. Then, thecalculation section 402 creates a third straight line indicating thecorrelation between the test recording powers belonging to the thirdtest recording power group and the products corresponding to these testrecording powers, and calculates a third gradient of the third straightline. Further, the calculation section 402 selects at least two testrecording powers as test recording powers belonging to another group oftest recording powers (hereinafter, referred to as a “fourth testrecording power group”) from the plurality of test recording powers. Thetest recording powers belonging to the fourth test recording power groupare selected such that an average of such test recording powers issmaller than the second average power. Then, the calculation section 402creates a fourth straight line indicating the correlation between thetest recording powers belonging to the fourth test recording power groupand the products corresponding to these test recording powers, andcalculates a fourth gradient of the fourth straight line. Then, thecalculation section 402 calculates a second ratio based on the thirdgradient and the fourth gradient.

Next, the calculation section 402 determines that a linearity of thevalue of exponent value corresponding to one of the first ratio and thesecond ratio, which is closer to ratio 1, is higher.

As described above, among the plurality of values of exponent n, thevalue providing the higher linearity may be selected.

The method for comparison on linearity in this embodiment is not limitedto the above. The calculation section 402 may perform the comparison onlinearity as follows. Regarding each of the plurality of values ofexponent n, the calculation section 402 sets one test recording powergroup including at least two test recording powers among the pluralityof test recording powers, sets another test recording power groupincluding at least two test recording powers among the plurality of testrecording powers, such that the test recording powers in the two testrecording power groups are not completely the same. Then, thecalculation section 402 creates a straight line for each test recordingpower group, and calculates the gradient of each straight line. Thecomparison on linearity may thus be performed.

In more detail, regarding the value of exponent of 2, the calculationsection 402 selects at least two test recording powers among theplurality of test recording powers, so as to set a first test recordingpower group including the selected at least two test recording powers.Then, the calculation section 402 creates a first straight line based onall the test recording powers of the first test recording power groupand the products corresponding to all the test recording powers of thefirst test recording power group, and calculates a first gradient of thefirst straight line. Regarding the value of exponent of 2, thecalculation section 402 selects at least two test recording powers amongthe plurality of test recording powers such that these test recordingpowers are not completely the same as those included in the first testrecording power group, so as to set a second test recording power groupincluding the selected at least two test recording powers. Then, thecalculation section 402 creates a second straight line based on all thetest recording powers of the second test recording power group and theproducts corresponding to all the test recording powers of the secondtest recording power group, and calculates a second gradient of thesecond straight line. Then, the calculation section 402 calculates afirst ratio based on the first gradient and the second gradient.

Regarding the value of exponent of 3 also, the calculation section 402selects at least two test recording powers among the plurality of testrecording powers, so as to set a third test recording power groupincluding the selected at least two test recording powers. Then, thecalculation section 402 creates a third straight line based on all thetest recording powers of the third test recording power group and theproducts corresponding to all the test recording powers of the thirdtest recording power group, and calculates a third gradient of the thirdstraight line. Regarding the value of exponent of 3, the calculationsection 402 selects at least two test recording powers among theplurality of test recording powers such that these test recording powersare not completely the same as those included in the third testrecording power group, so as to set a fourth test recording power groupincluding the selected at least two test recording powers. Then, thecalculation section 402 creates a fourth straight line based on all thetest recording powers of the fourth test recording power group and theproducts corresponding to all the test recording powers of the fourthtest recording power group, and calculates a fourth gradient of thefourth straight line. Then, the calculation section 402 calculates asecond ratio based on the third gradient and the fourth gradient.

The calculation section 402 compares the first ratio and the secondratio, and thus determines one of the first value and the second valuewhich corresponds to the higher linearity.

In the above, a plurality of methods for comparison have been described.In any method for comparison, when one ratio is equal to or greater than1 and the other ratio is equal to or less than 1, the calculation method402 may calculate the inverse number of the ratio which is equal to orgreater than 1 to make both ratios equal to or less than 1, and select avalue closer to 1 in this state. Alternatively, when one ratio is equalto or greater than 1 and the other ratio is equal to or less than 1, thecalculation method 402 may calculate the inverse number of the ratiowhich is equal to or less than 1 to make both ratios equal to or greaterthan 1, and select a value closer to 1 in this state.

The above-described plurality of methods for comparison on linearity aremerely exemplary. Any method may be used as long as the comparison onlinearity of the correlation can be performed.

As described in Embodiment 1, when the value of exponent n is 3 also,the recording power at which the product of the modulation factor andthe cube of the test recording power is 0 is a critical recording powerfor forming marks on the optical disc 101. When a recording power largerthan the critical recording power is used, the modulation factor ismeasured regardless of whether there is a tilt or not at the time ofreading. Therefore, the recording power at which the product of themodulation factor and the cube of the recording power is 0 is the sameregardless of whether there is a tilt or not at the time of reading.

Recently, optical discs including a plurality of recording films havebeen developed. In this embodiment, the value of exponent n can beappropriately determined for each of the plurality of recording films ofone optical disc.

In the recording power determination device 108 of this embodiment, theoutput section 402 outputs a signal to the recording section 210 suchthat the value, among the plurality of values of exponent n,corresponding to the highest linearity is recorded on the optical disc101. The recording section 210 records such a value of exponent on theoptical disc 101. The optical disc 101 may have an area for recordingsuch a value of exponent in advance. Alternatively, such a value ofexponent may be recorded in the user data area of the optical disc 101.In the case where such a value of exponent is recorded in apredetermined area of the optical disc 101 as described above, theoptical disc apparatus 100 having such an optical disc 101 mountedthereon reads the value recorded on the optical disc 101 for determiningthe recording power, and can determine an appropriate recording powerquickly using the read value without performing the comparison onlinearity.

Alternatively, such a value of exponent may be recorded on the opticaldisc apparatus 100.

In this embodiment, the optical disc 101 has identification informationrecorded thereon for identifying the optical disc 101. Theidentification information is, for example, information regarding thedisc manufacturer of the optical disc 101 or information on the lot ofthe optical disc 101.

The reproduction section 104 reads the identification informationrecorded on the optical disc 101, and outputs a signal 105 indicatingthe identification information to the recording power determinationdevice 108.

The signal 105 indicating the identification information is input to theinput section 401 of the recording power determination device 108. Thememory 404 of the recording power determination device 108 includes anidentification information storage section. After the value of exponentn of the highest linearity which corresponds to the identificationinformation of the optical disc 101 is determined from the plurality ofvalues, the calculation section 402 stores the identificationinformation of the optical disc 101, and the value of the highestlinearity corresponding to the identification information of the opticaldisc 101, in the identification information storage section of thememory 404.

The identification information of the optical disc 101, and the value ofthe highest linearity corresponding to the identification information ofthe optical disc 101, are stored in the memory 404. Therefore, when theoptical disc 101 is mounted on the optical disc apparatus 100, thereproduction section 104 reads the identification information of themounted optical disc 101, and the calculation section 402 of therecording power determination device 108 determines whether or not theread identification information is the same as the identificationinformation stored in the identification information storage section.When determining that the read identification information is the same asthe identification information stored in the identification informationstorage section, the calculation section 402 reads the value of exponentn corresponding to the highest linearity, among the plurality of values,from the memory 404, and can determine an appropriate recording powerquickly using the read value, without performing the comparison onlinearity on the plurality of values.

This embodiment is especially effective in an optical disc apparatusconformed to the BD format as in Embodiment 1.

As described in Embodiment 1, an optical disc conformed to the BD formathas a value of Pind, a value of ρ, a value of κ and a value of Mindstored thereon in advance. The reproduction section 104 reads the valuesof ρ and κ.

When the calculation section 402 determines that the linearity obtainedwhen the value of exponent n is 2 is higher, the calculation section 402calculates a recording power P500 shown in FIG. 12( b) and calculates arecording power Pw1 in accordance with the following expression 1.Pw1=P500×(−1/κ+2)×ρ  expression 1

By contrast, when the calculation section 402 determines that thelinearity obtained when the value of exponent n is 3 is higher, thecalculation section 402 calculates a recording power P600 shown in FIG.12( c) and calculates a recording power Pw1 in accordance with thefollowing expression 2.Pw1=P600×(3κ−2)/(2κ−1)×ρ  expression 2

The output section 403 outputs a signal 109 indicating the recordingpower Pw1 to the recording power setting section 110.

In the above description, the values of exponent n are 2 and 3.Depending on the structure of the optical disc or the characteristics ofthe recording film of the optical disc, the linearity may be high in thecase where the value of exponent n is neither 2 nor 3. In thisembodiment, the value of exponent n is not limited to 2 or 3, and may beany real number other than 1. For calculating the recording power, thecoefficients regarding κ and ρ change in accordance with the value ofexponent n. For example, when the value of exponent n is 0, thecalculation section 402 calculates the recording power Pw1 in accordancewith the following expression 2′.Pw1=P700×(1/(2−κ))×ρ  expression 2′

Here, P700 is obtained as follows. An approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products when the value of exponent n is 0 is created, andthe recording power at which the product is 0 on the approximate line isP700.

Incidentally, when the value of exponent n is 1, the recording power Pw1is calculated in accordance with the following expression as describedabove with reference to FIG. 22.Pw1=Pthr×κ×ρ

Pthr is obtained as follows. An approximate line indicating thecorrelation between the plurality of test recording powers and theplurality of products when the value of exponent n is 1 is created, andthe recording power at which the product is 0 on the approximate line isPthr.

In the above description, the comparison on linearity is performedbetween two values. This embodiment is not limited to this. In thisembodiment, the comparison on linearity may be performed among threevalues or more. For example, the value of exponent corresponding to thehighest linearity may be determined among three values of 2, 2.5 and 3.

According to this embodiment, the value of exponent n corresponding tothe higher linearity among at least two values is calculated based onthe correlation between (i) the test recording power and (ii) theproduct of the modulation factor and the n'th power of the testrecording power (n is a real number other than 1). Thus, an appropriaterecording power can be determined without relying on the range of thetest recording powers.

Embodiment 3

Hereinafter, Embodiment 3 of a recording power determination method anda recording power determination device according to the presentinvention will be described with reference to FIG. 14.

A recording power determination device 108 of this embodiment hassubstantially the same structure as that of the recording powerdetermination device described in Embodiment 1 with reference to FIG. 5.An optical disc apparatus 100 including the recording powerdetermination device 108 of this embodiment also has substantially thesame structure as that of the optical disc apparatus described inEmbodiment 1 with reference to FIG. 2. In order to avoid redundancy, therecording power determination device 108 and the optical disc apparatus100 of this embodiment will not be described regarding the points whichare the same as those of Embodiment 1.

The recording power determination method of this embodiment will bedescribed with reference to FIG. 13.

As described above, an optical disc 101 conformed to the BD format hasvalues of Pind, ρ, κ and Mind stored thereon in a predetermined area. Asshown in S32 of FIG. 13, the reproduction section 104 reads the valuesof Pind, ρ, κ and Mind from the optical disc 101. Then, the reproductionsection 104 outputs a signal 105 indicating the values of Pind, ρ, κ andMind to the recording power determination device 108.

As shown in S34 of FIG. 13, the recording power determination device 108confirms that the largest modulation factor among the plurality ofmodulation factors is larger than the value of Mind and that thesmallest modulation factor among the plurality of modulation factors issmaller than the value of Mind.

Before recording test data, the recording power determination device 108determines the test recording powers A through H such that thedifference between each adjacent test recording powers is equal to orless than 10% of the value of Pind.

After recording the test data at the test recording powers A through H,the reproduction section 104 measures the plurality of modulationfactors corresponding to the plurality of test recording powers. Thereproduction section 104 outputs a signal 107 indicating the pluralityof modulation factors corresponding to the plurality of test recordingpowers to the recording power determination device 108.

The calculation section 402 of the recording power determination device108 confirms that the largest modulation factor among the plurality ofmodulation factors is larger than the value of Mind and that thesmallest modulation factor among the plurality of modulation factors issmaller than the value of Mind. Specifically, the calculation section402 determines whether or not the largest modulation factor is smallerthan the value of Mind. When determining that the largest modulationfactor is smaller than the value of Mind, the calculation section 402sets a plurality of test recording powers larger than the previous testrecording powers, and the output section 403 outputs a signal 109indicating the newly set test recording powers to the recording section210. The recording section 210 records the test data at the newly settest recording powers. The reproduction section 104 reads the newlyrecorded test data, and the calculation section 402 again determineswhether or not the largest modulation factor is smaller than the valueof Mind. Until the reproduction section 104 measures a modulation factorlarger than the value of Mind, the calculation section 402 sets aplurality of test recording powers larger than the previous testrecording powers.

The calculation section 402 also determines whether or not the smallestmodulation factor is larger than the value of Mind. When determiningthat the smallest modulation factor is larger than the value of Mind,the calculation section 402 sets a plurality of test recording powerssmaller than the previous test recording powers, and the output section403 outputs a signal 109 indicating the newly set test recording powersto the recording section 210. The recording section 210 records the testdata at the newly set test recording powers. The reproduction section104 reads the newly recorded test data, and the calculation section 402again determines whether or not the smallest modulation factor is largerthan the value of Mind. Until the reproduction section 104 measures amodulation factor smaller than the value of Mind, the calculationsection 402 sets a plurality of test recording powers smaller than theprevious test recording powers.

In this manner, the calculation section 402 confirms that the largestmodulation factor is larger than the value of Mind and that the smallestmodulation factor is smaller than the value of Mind.

FIG. 14( a) is a graph illustrating the relationship between the testrecording power and the modulation factor. The calculation section 402confirms that the modulation factor corresponding to the smallest testrecording power H is equal to or smaller than the value of Mind and thatthe modulation factor corresponding to the largest test recording powerA is larger than the value of Mind as shown in FIG. 14( a).

Next, after confirming that the largest modulation factor is larger thanthe value of Mind and that the smallest modulation factor is smallerthan the value of Mind, the calculation section 402 calculates a productof each of the plurality of modulation factors and the square of each ofthe plurality of test recording powers.

FIG. 14( b) is a graph illustrating the relationship between (i) thetest recording power and (ii) the product of the modulation factor andthe square of the test recording power.

Next, referring to S36 of FIG. 13, the calculation section 402 createsan approximate line indicating the correlation between the plurality oftest recording powers and the plurality of products, and calculates arecording power P500 at which the product is 0 on the approximate line,as shown in FIG. 14( b).

Then, as shown in S38 of FIG. 13, the calculation section 402 calculatesa recording power Pw1 for recording user data based on the recordingpower P500 in accordance with the following expression 1.Pw1=P500×(−1/κ+2)×ρ  expression 1

The output section 403 outputs a signal 109 indicating the recordingpower Pw1 to the recording power setting section 110.

According to this embodiment, the relationship between the modulationfactor and the value of Mind is checked, and it is confirmed that thesmallest modulation factor is smaller than the value of Mind and thatthe largest modulation factor is larger than the value of Mind. By this,data is recorded at a test recording power in a range which is close tothe range of test recording powers used by the disc manufacturer fordetermining Pind. Therefore, the recording power recommended by the discmanufacturer can be more accurately obtained.

In the above description, it is confirmed that the smallest modulationfactor is smaller than the value of Mind and that the largest modulationfactor is larger than the value of Mind. A condition may be added thatthe smallest test recording power among the plurality of test recordingpowers is equal to or greater than 0.9 times the recording power atwhich the modulation factor is substantially equal to the value of Mind.With such a condition, data is recorded at a test recording power in arange closer to the range used by the disc manufacturer for determiningPind. Therefore, the recording power recommended by the discmanufacturer can be still more accurately obtained.

A condition may be added that the largest test recording power among theplurality of test recording powers is equal to or less than 1.1 timesthe recording power at which the modulation factor is substantiallyequal to the value of Mind. With such a condition, data is recorded at atest recording power in a range still closer to the range used by thedisc manufacturer for determining Pind. Therefore, the recording powerrecommended by the disc manufacturer can be still more accuratelyobtained.

Moreover, a condition may be added that the smallest test recordingpower is equal to or greater than 0.9 times the recording power at whichthe modulation factor is substantially equal to the value of Mind andthe largest test recording power is equal to or less than 1.1 times therecording power at which the modulation factor is substantially equal tothe value of Mind. With such a condition, the recording powerrecommended by the disc manufacturer can be still more accuratelyobtained.

The margin of the largest test recording power or the smallest testrecording power with respect to the recording power at which themodulation factor is equal to the value of Mind does not need to be 10%,as long as data is recorded at a test recording power in a range closeto the range used by the disc manufacturer for determining Pind.

As can be appreciated from the graph of FIG. 14( a), as the recordingpower becomes larger, the width of the marks formed on the optical disc101 increases, resulting in an increase in the modulation factor. Whenthe recording power reaches a certain point, the width of the marks isrestricted by the width of the track and thus saturates. Accordingly,the modulation factor also saturates. The magnitude of the recordingpower can be classified into three ranges in terms of the relationshipwith the modulation factor. In a first range of the recording power, themodulation factor increases with no influence of the width of the track(smaller than the test recording power H). In a second range of therecording power, the modulation factor increases while being influencedby the width of the track (from the test recording power H to the testrecording power A). In a third range of the recording power, themodulation factor saturates under the influence of the width of thetrack (larger than the test recording power A).

As shown in FIG. 14( b), with a recording power within the range fromthe test recording power A to the test recording power H, thecorrelation between (i) the test recording power and (ii) the product ofthe modulation factor and the square of the test recording powerexhibits a high linearity. By contrast, with a recording power largerthan the test recording power A or a recording power smaller than thetest recording power H, the width of the marks is determined bydifferent factors. Therefore, the correlation does not necessarilyexhibit a high linearity.

The range between the critical recording power for forming the marks andthe test recording power H is very narrow. With a recording power largerthan the test recording power A, it is difficult to detect a change inthe optimum recording power caused by an external disturbance since themodulation factor saturates. Accordingly, an appropriate range ofmodulation factor used for determining the recording power is a range inwhich the modulation factor changes while being influenced by the widthof the track.

A recording power is in the range in which the modulation factorincreases with no influence of the width of the track in the case where,for example, dust is attached to the optical disc 101 or the opticalhead 102; an external disturbance such as a relative tilt or defocusingoccurs between the optical disc 101 and the optical head 102; or thestrength of the optical beam emitted by the optical head 102 is reducedby a temperature change of the optical head 102. A recording power is inthe range in which the modulation factor saturates under the influenceof the width of the track in the case where, for example, the strengthof the optical beam emitted by the optical head 102 is increased by atemperature change of the optical head 102.

In the above description, when the modulation factor corresponding tothe test recording power H is larger than the value of Mind, a pluralityof test recording powers smaller than the previous test recording powersare set and test data is recorded at the newly set test recordingpowers. Similarly, when the modulation factor corresponding to the testrecording power A is smaller than the value of Mind, a plurality of testrecording powers larger than the previous test recording powers are setand test data is recorded at the newly set test recording powers. Thisembodiment is not limited to this. The recording power may be determinedusing only a predetermined range of modulation factors with the range oftest recording powers being expanded.

However, in order to expand the range of test recording powers, it isnecessary either to expand the difference between each adjacent testrecording powers or to expand the range used for determining therecording power. The former decreases the precision, and the latterextends the time until the recording power is obtained or wears the areaused for determining the recording power unnecessarily quickly.Especially in the case of write-once read-many optical discs on whichdata cannot be overwritten, it is not preferable to expand the area usedfor determining the recording power. Accordingly, it is preferable tomake a difference between each adjacent test recording powers equal toor less than 10% of the value of Pind, record test data so as to form 8Tmarks in a recording area equal to or less than one track, and only whenthe modulation factors are not within a predetermined range, newly set arange of test recording power to record the test data. With thisarrangement, the recording power can be determined highly preciselywithin a short period of time.

As described above, according to the recording power determinationmethod and the recording power determination device of this embodiment,an appropriate recording power can be determined.

Embodiment 4

Hereinafter, Embodiment 4 of a recording power determination method anda recording power determination device according to the presentinvention will be described with reference to FIG. 15.

In Embodiment 3, the first recording power is calculated based on therelationship between (i) each of the plurality of test recording powersand (ii) the product of each of the modulation factors and the square ofeach of the test recording powers. The present invention is not limitedto this.

In this embodiment, a case where the value of exponent is 1 will bedescribed.

A recording power determination device 108 of this embodiment hassubstantially the same structure as that of the recording powerdetermination device described in Embodiment 1 with reference to FIG. 5.An optical disc apparatus 100 including the recording powerdetermination device 108 of this embodiment also has substantially thesame structure as that of the optical disc apparatus described inEmbodiment 1 with reference to FIG. 2. In order to avoid redundancy, therecording power determination device 108 and the optical disc apparatus100 of this embodiment will not be described regarding the points whichare the same as those of Embodiment 1.

As described above, an optical disc 101 conformed to the BD format hasvalues of Pind, ρ, κ and Mind stored thereon in a predetermined area.The recording power determination device 108 of this embodiment issubstantially the same as the recording power determination devicedescribed in Embodiment 3, in that the recording power determinationdevice 108 confirms that the largest modulation factor among theplurality of modulation factors is larger than the value of Mind andthat the smallest modulation factor among the plurality of modulationfactors is smaller than the value of Mind. Therefore, the recordingpower determination device 108 of this embodiment will not be describedregarding the points which are the same as those of Embodiment 3.

FIG. 15( a) is a graph illustrating the relationship between the testrecording power and the modulation factor corresponding to the testrecording power. The calculation section 402 of the recording powerdetermination device 108 confirms that the modulation factorcorresponding to the smallest test recording power H is smaller than thevalue of Mind and that the modulation factor corresponding to thelargest test recording power A is larger than the value of Mind as shownin FIG. 15( a).

Next, after confirming that the largest modulation factor is larger thanthe value of Mind and that the smallest modulation factor is smallerthan the value of Mind, the calculation section 402 calculates a productof each of the plurality of modulation factors and each of the pluralityof test recording powers.

FIG. 15( b) is a graph illustrating the relationship between (i) thetest recording power and (ii) the product of the modulation factor andthe test recording power.

As shown FIG. 15( b), the calculation section 402 creates an approximateline indicating the correlation between the plurality of test recordingpowers and the plurality of products, and calculates a recording powerP1500 at which the product is 0 on the approximate line. Then, thecalculation section 402 calculates a recording power Pw1 for recordingdata in accordance with the following expression 3.Pw1=P1500×κ×ρ  expression 3

According to this embodiment, the relationship between the modulationfactor and the value of Mind is checked, and it is confirmed that thesmallest modulation factor among the plurality of modulation factors issmaller than the value of Mind and that the largest modulation factoramong the plurality of modulation factors is larger than the value ofMind. By this, data is recorded at a test recording power in a rangewhich is close to the range of test recording powers used by the discmanufacturer for determining Pind. Therefore, the recording powerrecommended by the disc manufacturer can be more accurately obtained.

In the above description, it is confirmed that the smallest modulationfactor is smaller than the value of Mind and that the largest modulationfactor is larger than the value of Mind. A condition may be added thatthe smallest test recording power is equal to or greater than 0.9 timesthe recording power at which the modulation factor is substantiallyequal to the value of Mind. With such a condition, data is recorded at atest recording power in a range closer to the range used by the discmanufacturer for determining Pind. Therefore, the recording powerrecommended by the disc manufacturer can be still more accuratelyobtained.

A condition may be added that the largest test recording power is equalto or less than 1.1 times the recording power at which the modulationfactor is substantially equal to the value of Mind. With such acondition, data is recorded at a test recording power in a range closerto the range used by the disc manufacturer for determining Pind.Therefore, the recording power recommended by the disc manufacturer canbe still more accurately obtained.

Moreover, a condition may be added that the smallest test recordingpower is equal to or greater than 0.9 times the recording power at whichthe modulation factor is substantially equal to the value of Mind andthe largest test recording power is equal to or less than 1.1 times therecording power at which the modulation factor is substantially equal tothe value of Mind. With such a condition, the recording powerrecommended by the disc manufacturer can be still more accuratelyobtained.

The margin of the largest test recording power or the smallest testrecording power with respect to the recording power at which themodulation factor is equal to the value of Mind does not need to be 10%,as long as data is recorded at a test recording power in a range closeto the range used by the disc manufacturer for determining Pind.

In the case where the value of exponent is 1, as shown in FIG. 15( b),the linearity of the correlation between (i) the test recording powerand (ii) the product of the modulation factor and the test recordingpower may not be as high as the linearity of the correlation in the casewhere the value of exponent is 2. Due to the difference in the set rangeof the test recording powers, the value of the recording power Pthr atwhich the product is 0 may fluctuate slightly. Therefore, in the casewhere the value of exponent is 1, it is preferable to record data at atest recording power in a range closer to the range used by the discmanufacturer for determining Pind than the range in Embodiment 3. InEmbodiment 3, the linearity of the correlation between (i) the testrecording power and (ii) the product of the modulation factor and thetest recording power is high.

In the above description, when the modulation factor corresponding tothe test recording power H is larger than the value of Mind, a pluralityof test recording powers smaller than the previous test recording powersare newly set and test data is recorded at the newly set test recordingpowers. Similarly, when the modulation factor corresponding to the testrecording power A is smaller than the value of Mind, a plurality of testrecording powers larger than the previous test recording powers arenewly set and test data is recorded at the newly set test recordingpowers. Alternatively, the recording power may be determined using onlya predetermined range of modulation factors with the range of testrecording powers being expanded.

However, in order to expand the range of test recording powers, it isnecessary either to expand the difference between each adjacent testrecording powers or to expand the range used for determining therecording power. The former decreases the precision, and the latterextends the time until the recording power is determined. Accordingly,like in Embodiment 3, it is preferable to make a difference between eachadjacent test recording powers equal to or less than 10% of the value ofPind, record test data in a recording area equal to or less than onetrack, and only when the recording power cannot be determined, newly seta range of test recording powers to record the test data. With thisarrangement, the recording power can be determined highly preciselywithin a short period of time.

In Embodiments 3 and 4, the values of exponent are 1 and 2. The value ofexponent may be any real number. In Embodiments 3 and 4, as describedabove in Embodiment 2, the value of exponent n may be selected such thatthe linearity of the correlation between (i) the test recording powerand (ii) the product of the modulation factor and the n'th power of thetest recording power is high. In this case, since the linearity of thecorrelation corresponding to the value of exponent n is high, therecording power at which the product is 0 is determined substantiallyuniquely even if the range of the test recording powers is wide.Therefore, an appropriate recording power can be determined in a shorterperiod of time. In this case also, it is preferable to record theselected value of exponent n on the optical disc. By recording the valueof exponent n on the optical disc, the degree of freedom of the discmanufacturer for designing the recording film can be enhanced.

As described above, in Embodiments 3 and 4, the value of Mind is readfrom the optical disc 101, and a product of the modulation factor andthe n'th power of the recording power is calculated referring to thevalue of Mind, so that an appropriate recording power for recording datacan be determined.

The optical disc apparatus of Embodiments 1 through 4 record data on theoptical disc and reproduce data recorded on the optical disc. Thepresent invention is not limited to this. The present invention isapplicable to any information recording apparatus for recording data ata plurality of test recording powers before recording data.

In Embodiments 1 through 4, the optical disc is used as an informationstorage medium. The present invention is not limited to this. Thepresent invention is applicable to any information storage medium forwhich the recording power is to be determined.

In Embodiments 1 through 4, the data is recorded by the Run LengthLimited (1,7) modulation system. The present invention is not limited tothis. According to the present invention, other recording systems may beused. In the case where modulation systems other than the Run LengthLimited (1,7) modulation system is used, it is preferable to record testdata corresponding to a signal indicating a great number of longestmarks and longest spaces of the system continuous to each other.According to the present invention, any single cycle signal may be used.In the case where a single cycle signal is used, it is preferable thatthe amplitude of the signal is about the same as the amplitude of thesignal of the longest marks and the longest spaces.

In Embodiments 1 through 4, the peak power (Pp), the bias power (Pe),and the bottom power (Pbw) are common among all the marks, and Tmp isalso common among all the marks. The present invention is not limited tothis. Other parameters for determining the recording power may be used.

In Embodiments 1 through 4, Ttop, dTtop, and dTe are classified intothree classes of 2T, 3T, and 4T or greater. The present invention is notlimited to this. Ttop, dTtop, and dTe may be classified by any othermethod.

In Embodiments 1 through 4, the ratio among the peak power, the biaspower and the bottom power is constant. The present invention is notlimited to this. The peak power, the bias power and the bottom power maybe independently determined. For example, the powers may be separatelydetermined such that the bias power and the bottom power are fixed whendetermining the peak power.

In Embodiments 1 through 4, test data is recorded at eight testrecording powers. The present invention is not limited to this. Thepresent invention is applicable to any case where data is recorded at aplurality of test recording powers.

In Embodiments 1 through 4, the recording power determination device 108determines the test recording powers A through H in advance. The presentinvention is not limited to this. The recording power determinationdevice 108 does not need to determine the test recording powers Athrough H in advance. The recording power setting section 110 may outputa signal indicating the test recording powers A through H set in thelaser driving circuit 112 to the recording power determination device108.

In Embodiments 1 through 4, the recording power determination device 108determines the recording power. The present invention providessubstantially the same effect even when the recording powerdetermination device and other peripheral elements are incorporated intoan IC.

According to a recording power determination method and a recordingpower determination device of the present invention, an appropriaterecording power can be determined, and therefore data can be propertyrecorded. In addition, an optical disc can be prevented from being,deteriorated unnecessarily quickly. The present invention is especiallyeffective in an optical disc apparatus conformed to the BD format whichrequires more precise recording power control for higher densityrecording.

While the present invention has been described with respect to preferredembodiments thereof, it will be apparent to those skilled in the artthat the disclosed invention may be modified in numerous ways and mayassume many embodiments other than those specifically described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention that fall within the true spirit andscope of the invention.

1. A recording power determination method for determining a recordingpower of an optical beam for recording data on an information storagemedium, the method comprising: a test data recording step of recordingtest data on the information storage medium at a plurality of testrecording powers; a modulation factor measuring step of reading the testdata recorded at each of the plurality of test recording powers,generating a signal, and measuring a modulation factor of the signalcorresponding to each of the plurality of test recording powers; aproduct obtaining step of calculating a product of an n'th power of eachof the plurality of test recording powers and the modulation factorcorresponding thereto, thereby obtaining a plurality of productscorresponding to the plurality of test recording powers, where n is avalue of exponent and is a real number other than 1; a first recordingpower calculating step of calculating a first recording power based onthe correlation between the plurality of test recording powers and theplurality of products; and a recording power calculating step ofcalculating the recording power based on the first recording power.
 2. Acomputer-readable medium embodied with a computer program for causing aninformation recording apparatus to perform the steps of the recordingpower determination method of claim
 1. 3. A recording powerdetermination device for determining a recording power of an opticalbeam used when a recording section records data on an informationstorage medium, the device comprising: an input section for receiving asignal indicating a plurality of modulation factors corresponding to aplurality of test recording powers; a calculation section forcalculating a product of an n'th power of each of the plurality of testrecording powers and the modulation factor corresponding thereto, so asto obtain a plurality of products corresponding to the plurality of testrecording powers, calculating a first recording power based on thecorrelation between the plurality of test recording powers and theplurality of products, and calculating the recording power based on thefirst recording power, where n is a value of exponent and is a realnumber other than 1; an output section for outputting a signalindicating the recording power calculated by the calculation section tothe recording section.
 4. An information recording apparatus,comprising: a recording section for recording data on an informationstorage medium using an optical beam; a reading section for reading thedata recorded on the information storage medium; and a recording powerdetermination device for determining a recording power of the opticalbeam used when the recording section records the data on the informationstorage medium; wherein: the recording section records test data on theinformation storage medium at a plurality of test recording powers; thereading section reads the test data recorded on the information storagemedium at each of the plurality of test recording powers, generates asignal, and measures a modulation factor of the signal corresponding toeach of the plurality of test recording powers; and the recording powerdetermination device calculates a product of an n'th power of each ofthe plurality of test recording powers and the modulation factorcorresponding thereto, so as to obtain a plurality of productscorresponding to the plurality of test recording powers, calculates afirst recording power based on the correlation between the plurality oftest recording powers and the plurality of products, and calculates therecording power based on the first recording power, where n is a valueof exponent and is a real number other than
 1. 5. A recording powerdetermination method for determining a recording power of an opticalbeam for recording data on an information storage medium, the methodcomprising: receiving a signal indicating a plurality of modulationfactors corresponding to a plurality of test recording powers; obtaininga plurality of products corresponding to the plurality of the testrecording powers, by calculating a product of an n'th power of each ofthe plurality of test recording powers and the modulation factorcorresponding thereto, wherein n is a value of exponent and is a realnumber other than 1; calculating a first recording power based on thecorrelation between the plurality of test recording powers and theplurality of products; and calculating the recording power based on thefirst recording power.
 6. A computer-readable medium embodied with arecording power determination program for recording data on aninformation storage medium, the program comprising: receiving a signalindicating a plurality of modulation factors corresponding to aplurality of test recording powers; obtaining a plurality of productscorresponding to the plurality of the test recording powers, bycalculating a product of an n'th power of each of the plurality of testrecording powers and the modulation factor corresponding thereto,wherein n is a value of exponent and is a real number other than 1;calculating a first recording power based on the correlation between theplurality of test recording powers and the plurality of products; andcalculating the recording power based on the first recording power. 7.An information recording method for recording data at a recording poweron an information storage medium after determining the recording powerof an optical beam for recording the data, the method comprising:recording test data on the information storage medium at a plurality oftest recording powers; reading the test data recorded at each of theplurality of test recording powers, generating a signal, and measuring amodulation factor of the signal corresponding to each of the pluralityof test recording powers; calculating a product of an n'th power of eachof the plurality of test recording powers and the modulation factorcorresponding thereto, thereby obtaining a plurality of productscorresponding to the plurality of test recording powers, where n is avalue of exponent and is a real number other than 1; calculating a firstrecording power based on the correlation between the plurality of testrecording powers and the plurality of products; calculating therecording power based on the first recording power; and recording thedata at the recording power.